Still listed as a series regular. And also, he's awesome. So I'm going to say no, he isn't dead. I hope not.

What episode because there is one where he almost dies from this poison us bullet.

nope he is not and no he isn't going to die.

~* SPOILERS *~
if you haven't watched them all, i suggest you don't read this [:

Derek actually is Alpha now. What i dislike about the werewolves in this series is that they they don't have a full transformation-- just a partial one. And only the "Alpha" is the one that can go full wolf. Also, the Alpha in the previous eps. looked like they used too much graphics on it.