there?s a funny story for that
The phrase deus ex machina (literally "god out of a machine") describes an artificial, or improbable, character, device, or event introduced suddenly in a work of fiction or drama to resolve a situation or untangle a plot (such as an angel suddenly appearing to solve problems).
Now that we got that out of the way, here is what I am thinking after reading chapter 313:
We got two things established already: Aizen is pretty much about to stomp on Karakura with seemingly no one close enough to stop him AND Orihimes powers are somehow increasing (as stated by Ichigo as he tried to stop her rushing towards Yachiru a few chapters back).
Now, here is what I think will happen:
Karakura will be destroyed, lots of people gonna die, probably even Keigo, Tatsuki and Mizuno(?), maybe even a lot of Shinigami when they rush to defend it (for example the remaining captains or vice-captains, or just the nameless bunch). At this point, Orihime would use her Event-rejection powers to simply turn back time and reject all of the events happening there, in essence undoing everything that has happened. Needless to say, that would take all of her "life force" and she?d die as a result, but would return one last time to Ichigo as a Shinigami.
That?s my fear for a really clich? ending of Bleach, and as of now, I see now other way to resolve the plot (if it?s supposed to end with the Winter War, or rather this one right here) than by using a Deus Ex Machina like this.