A young Master Xehanort is what this mysterious figure clearly depicts, and if I knew no different, I would say that he is definitely just that: Young Master Xehanort. But, I kind of have to piece this together from the battle in BBS. He wielded ethernal blades and not a keyblade, which reading through Master Xehanort's reports, he seemed to wield a keyblade from early on. Not to mention he performed all those ridiculous techniques that we haven't seen an enemy do before in Kingdom Hearts, so its pretty safe to say he's powerful. But, Unless he has some dual abilities such as having a keyblade AND ethernal blades, I'm going to go on and say this guy isn't who he looks like. Granted, we haven't actually seen him battling in DDD(if it's anything like BBS's battle, I'm going to cry), so this could thrown out at anytime. Just my two cents