They probably won't both die in the end. While they would if they were seriously going at it, without mercy or any interruptions, Kishi probably won't have it happen like that. Because Naruto and Sasuke are still friends deep down, you see, even if Sasuke refuses to admit it to even himself. Back then Naruto was letting Sasuke know that he wasn't going to stand by and let Sasuke achieve his revenge against the Leaf. He'd die protecting the people he cared about, even if he had to take down another.
#ofcourseKishiwon'tletithappenthatway.