Alternative on the pop scene is mostly dead. What people push as "Alt" or "Modern" rock nowadays (radio, not necessarily Internet radio), is really just poppy Progressive or Punk rock. (Evanesance, All American Rejects, please, shoot me). I really don't like this new music; I don't think many people really do.
As far as Alternative ever appearing again on the greater scene, I wouldn't doubt it; its a much loved music style, and look at how Classic Rock was revived in the 90's. There are still Alternative bands that play really well, (311, Radiohead(A cross-genre band id say), Weezer), although not all of them have altogether survived. Give it some time
