OK, let's see. After finally seeing the whole translations of "KH: 3D" scenes and understanding the whole story, there has been a few things that came to my mind and I want to share them with you. Let's see:

1º) The 7 Lights: There's a lot of discussion about the identities of these characters, but for me it's perfectly clear who they will be. The three original heroes (Terra, Aqua and Ventus), their "successors" (Riku, Kairi and Sora) and the one who connects both "generations" (Mickey). It's that simple. However, considering how Kairi has two roles (Princess of Heart and Protector of Light), who can assure us that there's only 7 of them? I explain in another part.

2º) The 13 Darknesses: It's really creepy that the New Organization XIII is formed by Xehanort's copies. Anyway, there's a few clues that can help us to identify who are the members of this new group. There are already 6 confirmed members: Master Xehanort, Young Xehanort, Ansem SoD, Xenmas, Xigbar and Saix. Who can be the other 6 non-revealed members and who will fill the 13th role after they failed to corrupt Sora? Let's see, all Xehanort's forms share two features: golden-yellow eyes and pointed ears. From the 13 members of the first Org XIII, only three of them (Xenmas, Saix and Xigbar) had those features; and they are been confirmed as members of the new Organization. Xaldin also had the pointed heads, but since he returned to be Dilan, I guess he saved himself from Xehanort's influence. However, it's obvious that the resistance to Xehanort's corruption left him exahusted. The rest of the members didn't have those features, so I think we can discard the "unseen-four" (Marluxia, Larxene, Demyx and Luxord) as possible members of the new Organization. As another possibility, since the battle against these guys will be the end of Xehanort's saga, I guess an epic end could be gathering ALL the main villains from the past as members of this new group, plus some extra surprises. See these candidates:
+ Master Eraqus: OK, this sounds weird, but I thought about it after remembering something. In Birth by Sleep, after Master Xehanort ended Master Eraqus, it's believed that his heart was transfered to Terra. So, if Master Eraqus' heart is inside Terra, that left his body empty. So I doubt Master Xehanort would let escape the chance of using this body (or Nobody) as his vessel.
+ Terra: Well, I think this was the first one in becoming a vessel for Master Xehanort, so this could be perfectly another of the non-seen-members of the new Organization XIII. However, if Terra is going to be one of the 7 Lights, I guess the good guys should recover Terra's body in order to bring him back, don't you think? It's a little confusing, honestly.
+ Vanitas: Considering he was Master Xehanort's apprentice in the whole plot from BbS, it's very possible MX used Vanitas as another of his vessels. Yeah, we saw him being destroyed, or did we? Light and darkness can't exist without each other, so if Ventus (light) survived to his last battle, I think it's obvious Vanitas did as well. Vanitas' yellow eyes can make more probable this idea, considering it's one of the features of all Master Xehanort's selves. Besides, for the big final battle, it would made possible to bring the Unversed as enemies again.
+ Absent Silhouettes and Data Replicas of the Org XIII: These were challenges from the Final Mix version of "Kingdom Hearts II", but it has been proven before that the Final Mix versions usually have cannon clues about what will happen in the future. The Unknown battle in KH FM (Xenmas), the Lingering Will battle in KHII FM (Terra) and the Unknown battle in KH BbS FM (Young Xehanort) are good examples. So these challenges from KH II FM could also work for the main continuity. I mean, these were replicas from the members of the first Org XIII, so Master Xehanort could use them perfectly as vessels for his new Organization. If we see more past members in the new Organization, these could work as an explanation about how is it possible. Don't you think?
+ Anti Black Coat: From all the Nightmares, this is the one who most confuses me. "A physical manifestation of the nightmare that Sora experiences while trapped in sleep". Honestly, I think this could work as the big leader of the others Nightmares. If Master Xehanort use it as one of his vessels, he could bring the Nightmares Dream Eaters for the big final battle.

3º) 7 Lights vs 13 Darknesses: Honestly, I don't find fair this. The good guys are outnumbered here, and if it was already hard enough to fight against just one at the time, each hero would have to fight against two Xehanorts at the same time. For a better way to defeat the new Organization XIII, I think there will be more that 7 protectors. The Trinity from the past (Ventus, Terra, Aqua), the Trinity from the present (Sora, Riku, Kairi) and the hero who connects them (Mickey) could get extra help from the others Keyblade Heroes we have seen in the series. Those would be the hurted Trinity (Roxas, Axel and Xion), the replicas of the main heroes (Data Sora and Riku Replica) and Namine (since she's Kairi's Nobody, she could use the Keyblade like Kairi; just like Roxas can use because he's Sora's Nobody). With these 6 extra heroes and the 7 protectors, we will have 13 Lights against the 13 Darknesses. A more equal fight, don't you think?

I have more to comment, but it would make the post too long. So I will wait to some answers and opinions, then I will post the rest.

I have a creepy theory , remember when vanitas and ventus fuse in one being to make a weak version of x blade ? and at the end of of kh 3 , the 13 and the 7 fuse in one entity ? xehanort plan is assume control of this ''one being'' because he put her heart pieces in the 13 darkness , but yen sid foreshadowing this , recruit kairi , one of the 7 lights , she have a strong heart and is one of princess of light , yen sid plan is make kairi assume control of this one being .

cool theory. But i think Kairi will be kidnapped again XD
Also i think that Lea didnt manage to block away Xehanorts heart and it went inside him. I think Lea is 13th darkness, all though i also hope im wrong. I also think that Roxas will help Sora and others.

nomura have to give a good excuse if marluxia and larxene are in the neo organization xiii , because they planned to make a rebellion in chain of memories and xehanort only put his hearth in the most loyal members .

I didn't expect answers so soon. Well, here you more points to talk:

4º) The Next Game: Considering all we have seen in "KH: 3D", I have a few ideas about which could be the next videogame in the Kingdom Hearts' series. The most logic thing would be thinking about "Kingdom Hearts III", but I have some interesting ideas for something previous to this:
4.1.) "Birth by Sleep - Volume 2": OK, Nomura has already said that there's still no plans to make this story, but they will have to do it sooner or later. According to what we saw in the video "A Fragmentary Passage", it must be about what it happened while the mains stories were in progress. For example:
- Aqua during the 10 years between "Birth by Sleep" and "Kingdom Hearts", possibly a story about how she protected the worlds and the characters destroyed by the Heartless that where sent to the Realm of Darkness. (As she found Cinderella's castle in it). We could see what happened to all those characters and how Aqua protected them until Sora's actions allowed them to be restored.
- Discovering what King Mickey was doing in the first videogame while Sora was travelling with Donald and Goofy. Some clips showed Mickey in the Realm of Darkness (maybe he found Aqua in that moment), Riku carrying Kairi at the Clock Tower in NeverLand, and Donald and Goofy about to enter by Traverse Town's doors for the very first time, before meeting Sora.
- Some extra videogame showing more non-seen events. There was some clips showing Kairi checking the mysterious mansion with the Twilight Town's trio (Hayner, Pence and Olette), DiZ (Ansem the Wise) doing something while Sora was sleeping after "KH:CoM" (possibly hiding his research inside of Sora), and Riku (with his blindfolded eyes) watching at Roxas and Xion while they walk across Twilight Town.
4.2.) The Secret Ending of "KH: 3D" ended showing that Yen Sid has summoned Kairi to train her since she can also use the Keyblade, to make her the last member of the 7 Protectors of Light. Curious, huh? Kairi can be both one of the 7 Princesses with Pure Heart of Light and one of the 7 Protectors of Light. So, I think the most logical thing to think is that before "Kingdom Hearts III", we could see a story of Kairi's journey to become a Keyblade Hero, or even a Keyblade Master. (Yeah, too soon when she's the less experienced one, but maybe her "princess" role can compensate her lack of fighting style. In the first game, Kairi's heart was inside Sora nearly all the time, so she must have learnt unconsciously some fighting moves in that time. A question is, which worlds could Kairi visit in her journey? I have been thinking, Sora has been in contact with Disney Heroes (Hercules, Aladdin, Peter Pan and even Mulan), Riku has been in contact with Disney Villains (Maleficent, Jafar, Hades, Ursula... etc); so it would be logical to think that Kairi will have contact with Disney Princesses. I guess in her journey, Kairi will visit the worlds of her Princesses partners, and maybe even another Disney Heroines, to get stronger from them. So let's see, she could visit Jasmine in Agrabah, Belle in Beast's Castle (maybe finally seeing Gaston in it), Cinderella in Castle of Dreams ("Cinderella III: A Twist in Time"), the same story for Cinderella III could work for the other Princesses (Snow White, Aurora and Alice), Mulan in the Land of Dragons, Ariel in Atlantica, Elizabeth Swan in Port Royal and even Wendy in NeverLand. If Sora knows about her journey, I'm pretty sure he would be worried about her (he's in love with her), so it would be interesting to see what Sora will do if he knows about Kairi's training. At the end, I think Kairi could even find a way to release Aqua from the Realm of Darkness, bringing hopes to release Ventus too; leaving just Terra to find. If Kairi finds Aqua's armour in Radiant Garden, it could suit her just like Ventus' armour dressed Sora in KH:3D, don't you think?

5º) The Dream Eaters: These characters has been really interesting for me, especially in their Spirit forms; maybe because they make me think about Pokemon? Anyway, they have proven to be the perfect partners for a Keyblade Hero; so I hope KH:3D won't be the last time we see them. Especially after seen Sora's last scene in the game. One of Disney's mottos use to be about "Make your Dreams come true", so it must be a way to make the Dream Eaters to exist outside the Realm of Sleep. I wouldn't be surprise if Sora's childish heart or Kairi's pure heart do that possible. The Dream Eaters could materialize in the real world by Sora's memories of his friends from previous adventures: Aura Lion from Leon or Simba, Kuma Panda from Mulan, Sea Horse Dragon from Atalantica... etc. I definetely want to see these guys again in the future, they could work as the protector guide spirits of the Keyblade Heroes or something, don't you think?

I'll wait before posting the next ones. So, what do you think?

DragonSeeker wrote:cool theory. But i think Kairi will be kidnapped again XD

I doubt that, because she was never an important character in kingdom hearts, yes she was one of the seven pure hearts of the worlds, but xehanort never thought about taking her, she was and still in a mere child.

Ok so it seems wwe already know most of the worlds in kh 3 thanks to 3d beast castle,castle of dreams,snow whites world,enchanted dominuion, wonderland.agrabah,radaint gardains,andKey blade graveyard,The world that ends with you world,castle oblivan/land of depataur. the other worlds is only speculations theycould be just cut sceans but still ill add them to the list Destany islands, Twikight town traveuse town with distict 6/7 ,and masteras tower along with TWTNW