Activision CEO Bobby Kotick quoted in this month's Conde Nast Portfolio saying that future versions of Guitar Hero will have "other instruments" and "vocals," and the crew over at Joystiq says that a source within Activision has confirmed that Guitar Hero IV will feature a microphone and drumkit, and that Activision is planning on pumping out new downloadable content as often as "weekly" once Guitar Hero: Aerosmith comes out in June.

Interview With Activision CEO - Executive Articles - Portfolio.com