[Sorry about all the posts, but when it rains, it pours!]
While I still have yet to beat Guitar Hero II on expert—hey, I have movies and TiVo to watch—it turns out that there will be yet ANOTHER Guitar Hero game coming out if this joystiq post is to be believed. And in just a couple months no less.
I'd assume that once they got most of the stuff for GH2 done, they said, "This version is perfect, lets just cover more songs and create new venues/skins and watch the money roll in."
This time we're are going to be lucky enough to get Guitar Hero: 1980's Edition and it will be coming out in "3-4 months." Perhaps the same time the Xbox 360 version of Guitar Hero II is released (which looks amazing by the way and is rumored to have an extra plug on the guitar for a potential distortion pedal attachment).
There isn't any information available yet about the possible track list. I'd assume that as more of these come out, they'll start having the same track on multiple games. Heck, I wish they had all the tracks from GH1 on GH2, there are so many good ones there.
While I don't own an Xbox 360 (and really am leaning towards just getting a PS3 whenever I get an HDTV) I am definitely drawn to the hotness of the game in high res and the possibility of downloading additional songs.
Really, I'm just hoping that I don't need to buy all new guitar controllers if I get the PS3. Some kind of adapter would be fine for me.