Board Thread:General Discussion/@comment-4161952-20130801170712/@comment-6904925-20130921122731

Aizen is a one of the 5 special war potential, so I think he will take part in this battle, question is which side will he take.

Also there is the fact that Aizen hasn't shown his bankai yet and Kubo doesn't leave something like that unseen, (remember Kaien shikai Kubo found a way to reveal that, even though Kaien was dead and the same with Chojiro bankai aswell).