Anything that becomes mainstream starts to sound repedative. Remember Nirvana being such a releaf to all those people? When the term "antisolo" was coined or just being used a lot... Well, within a few years that same style of music was sounding pretty tired wasn't it? A few of those people are still kicking around and still making music, but they're the Jerry Cantrells and Chris Cornells. Stone Temple Pilots and Pearl Jam, not The Dandy Warholls.

So in a couple of years it's going to be Nu Metal that's sounding prettty tired, and a few people will survive, but they'll probably be the true artists, not the imitators.

As for easy listening, their's always something heavier and harder. Early Death Metal circa the mid 80's is way heavier than Linkin Park or Staind, as is a lot of modern metal. Everything is relative.