Sasuke was just training/testing his new powers against white zetsu..That's why he told that he is going to test them outside too..In first sight i thought it was a Zetsu's clone but i really doubt it now..He hasn't changed his mind yet, so there is no way he will go against Madara at the moment..Also i think it too soon for a big battle again the main characters like Naruto vs Madara or Sasuke vs Madara.My prediction is that Sasuke will change only before his death in the fight against Naruto..