I think it's a safe bet to say that Maya will be one of the two heroes that is going to die. They've already killed off Alejandro and there's really no need to keep Maya on the show. I think Niki is a good possiblity as well. There's nowhere else they can go with her powers except to make even more personalities, and that would get old fast. Beyond that, if she died, it would be a good reason to bring D.L.'s mom into the story to help look after Micah (many believe that she's one of the original 12 from the picture).
That said, I must ask why everyone is so certain that Mohinder is going to die?! For one thing, he's not even a hero (at least, it hasn't been completely revealed yet if he is). Secondly, he's the freakin' narrarator, and even though he's done a *lot* of stupid things, he always redeems himself somehow (after all, he brought HRG back didn't he? He could've just let him die there). Thirdly, there are still a lot of places the writers could take his character.
Anywho, back to the subject...I doubt Hiro will die because he's one of the main reasons the ratings were so high in the first season. If they killed him off, they'd probably lose half their viewers and I doubt they're dumb enough to take that kind of risk. I think Peter is safe too, especially if they plan on bringing Sylar back into power, because whether you like him or not, you gotta admit that Peter is the only one who has even a small chance of beating the crap out of Sylar.
Anywho, that's just my take on it, but God knows I've been wrong about the show before, so who knows?

