Nathan died last season, and Sylar was made to think he was Nathan. In a recent episode, "Nathan" was murdered, and Sylar climbed out of the ground, apparently reawakened. So Nathan is toast. And for most of the season, it's been known that Hiro is already dying (brain cancer or a tumor; I forget which).
Of course, they could end up killing another male lead, but that would seem kind of excessive.
*SPOILERS*
Nathan died last season, and Sylar was made to think he was Nathan. In a recent episode, "Nathan" was murdered, and Sylar climbed out of the ground, apparently reawakened. So Nathan is toast. And for most of the season, it's been known that Hiro is already dying (brain cancer or a tumor; I forget which).
Of course, they could end up killing another male lead, but that would seem kind of excessive.