I've boiled things down to one of six theories.
1) Aizen will be able to make the Royal Key with some or all of KKT being sacked. He will enter the Royal Realm, only to get his ass kicked by the Royal Bodyguard (Who are all WAY stronger than him...)
2) Aizen does not get to make the key. Ichigo and Isshin somehow, due to the weirdness of the Dongai, come out before Aizen and Gin, and secretly are waiting with the rest of the KKT defenders.
3) Someone in Fake KKT realizes what's going on, blasts the columns holding the spell and the towns swap right in front of Aizen's weird-ass face. Which serves the bastard right (I'm getting sick of Captain Broken.)
4) Ichigo and Isshin show up, beat on Aizen a bit, he whacks them both down, and as he gloats, preparing to sacrifice the entire town, when he's cut in half by a familiar orange field. Pan to Orihime, now completely on her game, neatly saving all of existence in front of the astonished Kurosaki boys. Thus cementing her as A) Useful as all hell and B) Finally out of her eternal funk!
5) Series ends on a downer as Aizen destroys all of existence to try to be come God.
6) All of this entire arc is nothing but Aizen planning out his final plan during the original SS arc. We end with him deciding that it's worth it to try. However, he underestimates Ichigo's power, and instead of blocking him with one finger, he gets his head chopped off.
Yeah, a little strange, crazy or what have you. But this is all I got right now. Oh, and if this is way off base, please delete.