Still need a reason to pony up more money for another version of Guitar Hero? Well it seems that Red Octane has informed GameSpy that the 360 version of Guitar Hero 2 could support online play through a downloadable patch:

However, online multiplayer may not quite be dead yet. According to Red Octane, multiplayer is something they really wanted to get in the game, and may still add via an update down the road. The key, it seems, is co-op play, which is a lot trickier to make work (the pro-tourney mode is essentially two players independently playing against the computer, while co-op requires direct interaction between the players). So, while Red Octane isn't making any promises, we're holding out hope that multiplayer might still show up at some point. 

Oh man, make it happen. Having online battles or co-op would make the 360 version so much more uber -- not to mention we already know there's gonna be downloadable songs.