My prediction in this case is,Obito and Madara would go on and fight and probably Sasuke will join in.Then he will defeat the Juubi with some unneeded help from the alliance.After that Obito would go after Sasuke and they would fight in the other dimension,thus leaving Madara himself against the WHOLE ****ING WORLD!And without a doubt he will be sealed off with a lot of effort and finished,meanwhile Obito will explain to Sasuke about his pretending to be Madara,after which Sasuke would completely go WTF because he is getting mind****s from everyone aand NOBODY is telling him the right thing to know.So Obito turns out to be the one who knows everything and he explains to him the truth about Itachi.Then Sasuke,without thinking because as I said before,he was getting mind****ed,he would join him and they both would go back to the battlefield and fight against Naruto and the alliance.Sasuke would take on as usual Naruto and Obito would fight off the alliance.A lot of people would die leaving fewew countries to exist.But he wouldn't take the pressure and eventually,that's right...DIE!!!(I really like Obito,but...the odds...meh...).Then Naruto would defeat Sasuke with the remaining of the alliance and bring peace between them.Then everything would end and Naruto would become Hokage,because of his huge help of taking down the Juubi,thus surpassing his mother and father and becoming the sixth Hokage.The end!