this and then bolt steps up to revenge him
I don't think Revenge will ever come to the mind of any of Naruto's kids, simply cuz it's what Naruto tried to put an end to.
That said, with where the world was progressing, it wouldn't be impossible for Naruto to be killed.
Case 1 - Iron Man in the Avengers movie: He nearly sacrificed himself by diverting a missile (armed with a Nuclear Warhead) to another dimension. He survived because he got pulled (slowly) back to Earth (by gravity? cross-dimensional gravity?).
Case 2 - Superman in Man of Steel: He pulls off a similar stunt as Iron Man, but without the dimensions.
Case 3 - Batman in one of his Dark Knight movies (I forgot the exact one, can't be bothered to Bing): He also carried a weapon of mass destruction off in his aircraft, shown exploding later.
Exhibit A: Naruto's world has developed enough to feature smartphones and MacBook pros. While Ninjas may opt to use chakra instead, the Land of Iron may opt to develop weapons of mass destruction instead (think: Fission and Fusion bombs)
Exhibit B: Naruto's world has shown dimensions, and Naruto can't travel through them.
Conclusion: Naruto could easily die in one of those circumstances. In the case of dimensions, he could get shifted to a dimension where he could be trapped for years, coming back at the end of his sequel (even if briefly), to help his kids against their opponent (he could be to the what the sage was to him and Sasuke). Otherwise, he could get sent to a future/past where he'd realize that he was actually Kaguya's unnamed lover. Okay, that last one is a joke. lol.