User blog comment:Xilinoc/Ch. 617 - Return of the God/@comment-4207271-20150226143749/@comment-1248963-20150227070239

That's an interesting theory, and if the part about Kenpachi becomes true, it could be connected to the Special War Potentials (five of them, of which we don't know two?). In which case, Rangiku would fit too. Remember Gin said Aizen took something from Rangiku, what if it was a piece of the Soul King? By taking it onto himself, Aizen would become a War Potential too (assuming that having a piece of the Soul King in you makes you a War Potential)