User blog comment:Xilinoc/Ch. 618 - The Dark Arm/@comment-5693502-20150305120901/@comment-24531362-20150305140211

Methinks Aizen has some secret Aizen-knowledge that would've let him assimilate with or replace the Soul King, without the whole 'world-falling-apart' issue. Also, Uryu and the Ritter Force 5 are probably chilling at the bottom of the stairs, drinking RC Cola and having a friendly chat with Ichibei.