I still think it would be Maleficent. I mean, she's manipulative, powerful, and smart enough to know what she's doin. Plus, we don't know for a fact Braig is ever coming back. It was stated that if u destroy someone's heartless and nobody in the right order their sombody will resturn. And since Nomura is going to put a close to the "Xehanort Saga" Xehanort needs to return and be defeated forever (unless Nomura makes him return which I doubt). So with this said, Sora defeated Xehanort's Heartless (Ansem SoD) first in KH1, then Xehanort's Nobody (Xemnas) in KH2. Sothe order must be Heartless ---> Nobody to return a somebody. We don't know if Sora even defeated Braige's heartless. Don't get me wrong there's a possibility Sora did, but i doubt it personally. With that said, Braige might not even return! While Maleficent is still around ready to strike her revenge on Sora and attempt to rule the world. However, I do know that she may be dead along with Pete because she was last seen at the Castle That Never Was before it was destroyed. But i don't think Nomura would end Pete and Maleficent just yet.