Yeah I just don't see Sasuke fighting alongside the Shinobi Alliance.. It is entirely possible for it to go in that direction, but think about how much Kishi would have to include in each chapter. Nearly every character in the whole Narutoverse in one battle? I could be wrong, but I don't think so. I think Sasuke needs to prove to himself, that he is strong enough to back up his 'decision', whether it be to destroy the village or to help in the war. Either way, I think Hashirama will prove his strength to Sasuke, and somewhere along the way Sasuke will turn his anger towards Madara. I think it's better if the Shinobi alliance takes care of Obito + Madara first, and then Sasuke joins to take down the Juubi.