It's possible that Madara is poised to take over the roll of the big bad for the series now. Now that he's free to do what he wants, he may turn on Tobi and try and take the Ten Tails for himself. And then Naruto has to deal with Madara instead of Tobi.
Those guys are all other villains though(also, Oro is dead and sealed in a ghost jug). So why would they help defeat Madara?
Unless Sasuke somehow finds out that Madara is actually responsible for Itachi's death somehow, there's no reason my Sasuke would suddenly fight against him.
Unless he pulls a "I'm the only one allowed to destroy them!". Which I guess I could see. Tobi or Madara casts the Infinite Tsukiyomi, and Sasuke's EMS protects him from it, and he's the only one able to stop them. But he only does it because they are denying him his vengeance.