With the Juubi now dead and Obito practically washing up. Madara being Edo also being under the control of Kabuto/Orochimaru along with the four kage. Orochimaru could be the only possible villain if it wasn't for Sasuke. But, let's be honest when Sasuke came back saying he would "become hokage" he really meant it, having heard the full story from Hashirama. So, all in all.. It has to be Orochimaru.