I doubt Kakashi will die.
He's already died, for one. There would be absolutely no point in killing him off again.
Two, already said, but Sakura still has yet to surpass him... Or anyone else for that matter.
Three, Jiraiya's died already. That was Naruto's biggest teacher for the most part, other than Killer Bee and the toads. Iruka hasn't really made Naruto stronger. He trained him in the basics, and though Naruto and Iruka are like brothers (apparently), he hasn't given Naruto the big leap of improvement like Jiraiya did in the time skip with "that jutsu" or Kakashi with Rasenshuriken, or the toads with Sage Mode, or Killer Bee with the Kyuubi. If you kill off Kakashi as Naruto's main teacher, the mushy ending we expect Naruto to have will be tarnished. You already know, as good as this manga is, it's going for a "happily ever after" ending.