User blog comment:Lemursrule/THE ARRANCAR ARC IS OVER!/@comment-1211470-20100928105600/@comment-1268838-20100928162141

That's a tough one. I personally wouldn't consider it deus ex machina, because it doesn't contradict anything that Aizen had already said or done, and it wasn't outside of his character to take such a precaution, being as calculating as he is.