User blog comment:Godisme/The ever evolving Sosuke Aizen/@comment-1405841-20100910220741/@comment-1454424-20100913054211

The Hogyoku could be the devil. More specifically, Aizen's Hogyoku could be the devil. Remember how Aizen tried to complete his Hogyoku. He fed it souls, hundreds of souls! Yet the Hogyoku wasn't satisfied. Those were Aizen's words. In short, Aizen's Hogyoku demands things and as far as I can make out, Aizen's Hogyoku has not yet gave anything back for all the demands it has made.

By contrast, Urahara's Hogyoku has been quietly granting wishes without expecting or getting anything back. Urahara sealed it away and tried to destroy it but it still helped Urahara with Shinji and Co, awakened Orihime and Chad's powers etc, etc.

So I can see Aizen's Hogyoku taking over Aizen's body and becoming the devil and the main villain for the next arc. There could be some interesting plot points with the new villain having multiple personality disorder and being a "good guy" when the will of  Urahara's Hogyoku dominates and evil when the will of Aizen's Hogyoku dominates.