We have to take anything we saw / learned in "five years gone" with a grain of salt. But one thing we did learn was that Future Hiro had altered the course of events and the city still blew up.

Peter may control / supress Ted's power if he can concentrate - There's no guarantee that anything will happen without the presence of Ted.
Peter has a backup plan - Claire is to shoot him to prevent him from blowing.
Sylar has now embraced the idea of blowing up the city - Standing on a rooftop with 'ted' hands "Boom!"
Nothing Isaac painted proves the identity of the exploding man. Keep that in mind.
Peter dreamed of flying - He also dreamed of talking with Charles - Who was comatose.

All i'm saying is that at this point we can't know for sure.

Isaac has been kind of spot on but some of his works are open to interpretation i guess. I'd have to say that nothing is set in stone and the future can be changed. Given that Hiro set in motion a series of events with "save the cheerleader, save the world". Also in 'Five years gone we stil have no real proof' - only what the characters sa and believe.