I don't think any artists should live for ever. Immortality is incredibly cruel. You have to watch all of your loved ones die, and with musicians, when compared to forever, their music would only be known for a tiny part of the timeline. It would be cruel to make anyone lose everything except life, because they would get to the point where they'd want to die. (And I believe that people should have the right to death.)
As to the ones who should die... Well, we all die eventually. But if you mean who should die like, in the susunod twenty seconds... Eh, no one, again. No one "should" die. Same as people deserve the right to die, they deserve the right to live.
Artists who should live forever: Nelly Furtado, Lady Gaga, Taylor Swift, Katy Perry, Evanesance, Justin Bieber & Ke$ha. I don't really like the artists who should die thing, it can hurt other peoples feelings badly.