I think it will has something to do with the rest of the tailed beasts. Right now, all of the Tailed Beasts trust Naruto and believe that he is the reincarnation of the Sage of Six Paths. Madara is going to start sealing them, and they will likely opt for someone like Naruto (or Gaara in the Case of the One Tail) rather than being sealed inside Madara.
As for when, I have no clue. If Naruto and Sasuke are going to eventually have a final showdown, Sasuke already has a lot of catching up to do. Therefore, Naruto really can't get too much further ahead of Sasuke. Naruto already has his Kyubi-Sage Mode, which should be able to combat Madara's boosted forms. Naruto has been dividing his power evenly amongst all of the Shinobi Alliance, and also hasn't really taken a break since before his training on the island. I'm thinking that somebody like Juugo, Karin, Sakura, or Tsunade could come in handy at this point to restore Naruto's stamina and chakra. Furthermore, with their current relationship, Kurama and Naruto should be able to further perfect their merging.
However, Naruto really shined while fighting Obito. Perhaps it's Sasuke's turn to be the hero. He has a lot of redeeming to do, too.
