This corresponds with information Joystiq has received from a source close to the company, who tells us that multiple instruments – including a microphone and drumkit – will be a part of the next Guitar Hero game, likely to be called Guitar Hero IV despite its focus on multiple instruments (other potential names: Band Hero and Rockstar Hero). Also, our source reports that Activision insiders are proud enough of their drum peripheral to say that it will be "superior" to Rock Band's (we know, shocking).
Perhaps just as importantly, Activision's weakness in downloadable content could be resolved as early as the release of Guitar Hero: Aerosmith this June, when content is expected to be released regularly, perhaps "even weekly." Also contributing to the company's positive outlook on DLC is the pending merger with Vivendi, potentially giving it unparalleled access to that company's Universal Music Group, the largest family of record labels in the music industry.
We've asked Activision to comment on this story. If anyone close to the story has any additional information to share, you know where to find us.