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.

Well, seeing as Nobodies grow hearts now, it shouldn't be too hard to bring him back...put some things in about how Roxas had no memories, and so the heart he grew was original and his, yet he was still connected to Sora...it could happen. It would be a little obnoxious to have Roxas and Ven though.

 

But apparently, since Xemnas is unique enough to come back and be one of the thirteen darknesses, I don't see why Roxas can't be a light I mean Xehanort is almost cheating using his heartless and his nobody.

 

The Xemnas and Ansem in 3D are from separate timelines brought back by Young Xehanort, and according to Nomura Roxas never grew a heart it was Ventus' the whole time

i think this hole "nobodys grow hearts" was actually to bring Roxas back, since if he has his own heart, he could return and be one of the lights. However, Nomura and his team will have to find a way to explain exactly why it was sayd that Roxas held half of Sora and his power, in a way that Sora won't be affected.

And it's "possible spoilers", imagine if they were "major"!