Man, Activision is just churning these Guitar Hero games *out*! GameSpot has word that Guitar Hero: Metallica is due the first quarter in 2009 based on an SEC filing:

“In fiscal 2009, we plan to publish Guitar Hero: On Tour for the NDS; Guitar Hero: Aerosmith, Guitar Hero: Metallica, and Guitar Hero IV across multiple platforms,” the company said in its report. Activision’s fiscal year ends on March 31, 2009, which means that the game will likely follow the holiday release of Guitar Hero: World Tour (nee Guitar Hero 4).

And when he says “across multiple platforms”, we can only assume he means every possible platform including PS3, 360, Wii and even the beltbuckle.