WOW always has people leave and come back. Really it's a mere pinprick in an elephant... Then they'll have Blizzcon and start the hype machine for the next expansion.

I do think many have become bored of WOW and are just out there trying new things. That's what I've been doing. Rift is a good game that I am still subbed to but it really is WOW's wannabe brother with nicer graphics and a few gimmicks. So people looking for something refreshing usually leave fairly quickly because it's the same grinds as WOW only MORE grindy.

SWTOR will be huge and no telling what will happen with it. But it isn't out and people don't quit games for games that aren't even out yet. Got my preorder in!