I won't be surprised. I know I had a VEN IS A KEYBLADE LOLOLOL theory before BBS came out, and look at what Nomura gave us uh. THE LESS SENSE IT MAKES, THE MORE LIKELY IT'S CANON. Nomura seems to be shooting for "YOU THINK THAT PERSON IS HELPLESS AND INNOCENT? :DDD /PROVES WRONG" lately in games. I mean look at our final boss / one behind it all pattern so far;

KH1; Ansem, Seeker of Darkness
CoM; Marluxia
KH2; Xemnas
Days; Xion
BBS; Master Xehanort/Vanitas (but you still fight your best friends possessed as a final boss)
coded; []

I. Would not be surprised if by 3D, KAIRI is the final boss.