I'm still waiting for two more vials of the "super juice" to be found. (Perhaps in Nathan's liquor cabinet) that would bring Hiro and Peter back to normal.Actually that may not work. Remember when Claire cut off her pinky and it grew back in like 5 seconds? I think Sylar could regen the whole body even if the brain is the only thing left.
BTW, I wonder what would happen if Peter touches Sylar? Is Peter going to get all Sylar's abilities? A random abilities? Or Sylar's original ability to take other people's abilities? It is so confusing.