User blog comment:Godisme/Hear.Fear.Here/@comment-5306073-20120720131838/@comment-2248897-20120720184200

I think that bringing out the Royal Guard out the blue would be too much of a deus ex machina so I doubt it will happen. It can't be Isshin because it wouldn't make any sense for him to hold his sword to Urahara's head. Aizen isn't completely unbelievable but it seems unlikely that the Soul Society wouldn't notice such a powerful being escaping from their maximum security prison.