I'm almost salivating for a Shinji/Aizen fight. No idea about the victor though. And it would really be awesome if Orihime ended up being the one to defeat Ulquiorra, but I'm not holding my breath. :/
As for the rest, I'm going out on a limb here: I don't think that's really Aizen (or Tousen or Gin) with those three espada. With that many captains and lieutenants in one spot, Soul Society has what as a defense now? Kira? Himamori? It would be too convenient for Aizen/Tousen/Gin to just waltz right in and take over in their absence. And Aizen has already demonstrated how he just uses the espada to keep his enemies busy, so I'm betting he doesn't care one bit about the outcome of the current massive fight.