I'm not the biggest Heroes fan. In fact, I've only seen the last few episodes. But I did catch tonights episode set 5 years in the future. In it Hiro and Ando meet the future Hiro after the bomb (Sylar?) went off in New York City.
Now, maybe I watch too much science fiction, and maybe I'm too much of a Dr. Who fan, or perhaps I've seen too many Stargate episodes, but what happened (traveling to the future as Hiro and Ando did) shouldn't/couldn't have the same results as the episode showed.