Sounds like a fusion of Xehanort's Heartless and Xemnas. Is that possible? Come to think of it was it ever explained what happened when Xehanort's Heartless was blasted out of Riku when DiZ's machine exploded?
The more I think about it the more a merging of Ansem and Xemnas makes sense, that guy in the trailer could be the original Xehanort, reborn or remerged or something.
