My theory conflicts with Nomura's claims, but what the hey...The Sora/Roxas looking character is neither of them, but instead the son of Sora. (AND HE DOES NOT DIE IN THE VIDEO. HIS EYE TWITCHED)The girl with blue hair is the daughter of Riku.The old guy is Xenonhort's heartless once again...The man in the very end is none other than Sora himself!