http://www.youtube.com/watch?v=72niMyAvjh0 This is a trailer for the upcoming Guitar Hero Metallica. you can watch this trailer in GH:WT MoP is playing in the background. That alone is enough to buy this game.
I don't see the point of this? I mean they have World Tour coming out, why another game. This should be an expansion.
This isn't scheduled to come out til winter 2009 or possibly later. There has been wide speculation that Actvision will continue with 2 lines of guitar hero games. One will be the regular guitar hero games, and another will be guitar hero: world tour games with some subscript title to go with it(ex. Guitar Hero: World Tour 80's Edition).