I know people always are asking this question but I'm really eager to know
I hope not. A semi-permenant death of a major character is what made me like the Ultimate Universe. It gives the stories weight. If Peter comes back, takes an alternate (yet Spider-themed) identity until he re-replaces Miles, I'll flip out.
No way! If marvel wants Peter Parker back they will do it in the 616 or Now! whatever you want to call it. In the Ultimate universe it will be Miles. He's awesome so I hope he makes it 700 issues! They already started another "marvel universe" to cover peter parker as ultimate spider-man to match the tv show. So miles is even safe from that. Miles is also my favorite marvel character.