Actually, we don't know yet. The Shippuden series hasn't even gotten the Fourth Great Ninja War into full swing yet. Naruto is currently on a ship going to meet with the Eight Tails, so he can learn how to control his Nine Tailed Beast power. He hasn't even come close to the battle with Sasuke yet. And when it happens, he'll be fully prepared to die, but I don't think that'll happen.
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Watch Episode no 133, 134 of Naruto 1st season during the fight of Naruto and Sasuke this scene comes in...
It's like 30 episodes long, starting when Naruto and Sasuke fought each other in the hospital to when Sasuke beats Naruto and leaves for Orochimaru.
Naruto summons Gamabunta at the very end of Naruto episode 56, but they introduce themselves to each other in episode 57
You'll have to forgive me for not knowing the exact episode numbers, but Sasuke and Naruto fight several times in Naruto Shippuden for brief bits of time. Also know that this may contain SPOILERS. First, Naruto and Sasuke begin to fight in the first episode (which is actually just a teaser for what happens in the second story arc) until Orochimaru arrives and stops Sasuke from progressing any further. Then, when the actual story arc that I just mentioned happens, you see that scene play out a little further. After that, Sasuke and Naruto don't really fight or see each other again for a long time. In the manga, however, there is a chapter where Naruto and Sasuke really begin to fight after Pain has destroyed the Leaf Village and Sasuke was trying to disrupt the Hokage Summit. However, at that point Madara came to prevent Sasuke from going any further. As of now, in chapter 517 of the manga, Naruto and Sasuke have not fought again since then, but it's told to us that they will fight relatively soon-ish, and it'll be EPIC!! For now just continue to enjoy the story as it unfolds, because it's amazing right now.
Sasuke sees Tobi when he fights Deidara. Tobi flees after Deidara self-detonates. However, after he kills Itachi, Sasuke meets Tobi, who reveals himself as Madara Uchiha. The Shipuden Episode is 139.