Here is my guess...
The guy we see at the end, with the brown hair and eyes that turn orange, is Xehanort. Therefore, the next installment will be a prequel, or will at least have prequel flashbacks.
The old guy is someone who took over Xehanort's body, hence turning his hair silver, and thus giving him all those superpowers that are mentioned in the Ansem Reports.
The guy the old dude splits into might just very well be some other type of "puppet-like" person, that is being controlled by the bald man (kind of how Ansem controlled Riku, giving him the awesome duds.)
This theory makes a lot of sense, and I wouldn't be surprised if the above picture is the exact correct theory. All the clues match, even down to the fact that the eye that Riku has on his Souleater is also present on both the old man's keyblade and that of his "assistant".
XI Wiki


