Oishii from KH13 has translated a question from the interview. Please note that this contains spoilers about the Mysterious Figure and Young Master Xehanort.
--Other than Fantasia's world, there is the appearance of a character wearing a black coat and has gold eyes. Who is this character?
Nomura: In KH Birth By Sleep Final Mix we added a boss, a mysterious man who can manipulate time. That's him. KH3D will talk about what sort of person he is. For instance, where he will go in the future, and the appearance of Vanitas, we will see some appearances of this person of darkness.
MF is Young Xehanort who somehow used time to travel back to the BBS timeline . Nomura's statement.
hey, correct me if I'm wrong, but the fact that we killed all organization members could bring all of them back, no? it's the main reason why Xehanort's coming back, since we destroyed his nobody and heartless... and since organization members' heartless's could look like pretty much anything, since Xehanort's heartless was special (told in Re: CoM), we could have destroyed, without knowing it, their heartless's.
what about a Sora becoming possessed after a dream confrontation with, I don't know, Vanitas, young Xehanort, or whatever? It'd be an easy way to make him turn evil