The new issue of Game Informer Magazine has the scoop, reported by a poster on the NeoGAF forum and picked up by Kotaku: Guitar Hero IV will feature drumming and vocals. What an original idea!
To be totally fair, it does seem like a logical next step, and it's not like Harmonix invented the idea, either. Drum and guitar sims have existed in arcades in both Japan and the West for a long time now. Still, it's hard not to look at this with a cynical eye when you consider that this will come out roughly a year after the release of a successful game that already did a great job with the same thing. It will be released by a company that didn't do such a hot job with a similar product - Guitar Hero III was not just a bloated, garish sellout, it also felt rhythmically wrong somehow, like they weren't even bothering to keep time when they construct the note charts. To top it off, there's no way this will be compatible with Rock Band's drumkit, so you'll have to shell out another $200 for another set of plastic drums. Even if it manages to improve on some of the problems with the Rock Band kit - specifically, noise and sturdiness - it's still tough for the average gamer to justify.
The article also says there will be a create-a-song feature in GHIV, which sounds admittedly cool on its surface. But ultimately we'll have to see how actually functional it is; composing a full song with only five buttons might be more trouble than it's actually worth.
But Activision does show that they're still on the forefront of musical taste with their lineup of already-announced artists for the new game: Van Halen, the Eagles, Linkin Park, and Sublime! It's like a frat party in 2001!