I say sasuke, because the last fight that would be signing the end of the manga would be Naruto vs Sasuke, so before this fight, sasuke has to become godly powerful to make a suspense (if naruto will or will not defeat sasuke).
In other word, sasuke will beat madara and will take his eyes, becoming extremly powerful and then putting the table for the greatest fight ever, the valey of the end take 2.