Listings all over online retailers (Amazon & Gamestop specifically) are showing that Guitar Hero: Warriors of Rock (formally Guitar Hero 6) will be in stores on September 21.
GuitarHero.com now has a splash page showing the Guitar Hero: Warriors of Rock logo, and a link to pre-order at Gamestop.com. The game will be available for Wii, PS3 & XBox 360 in a standalone game, bundled with a guitar, or in the Super-Bundle (which would presumably include a guitar, drum set, microphone along with the game).