Not officially announced or w/e but sources say it's coming. it's also listed on IGN.com as an activision title. I would say that it would probably be released summer of 09 like he Aerosmith version to hold people over for the next full GH game which would probably be released winter of 09. anyways just a heads up. I will keep you posted.

They should release it late first quarter of 2009, not the summer... That's too close to next game I think

Here's a time line for you.

GH2 ps2 released nov 7th 2006
gh80's ps2 released Jul 24th 2007 8 months apart

GH3 360 released Oct 28th 2007
GHA 360 released Jun 29th 2008 also 8 months apart

GH4 360 TBR Oct 26th 2008

So w/ that we can assume GHM to be released around june-july 2009. (summer time)

fuckin the next 2 guitar heros look so badass. create a rocker, create a track. and then my fuckin second fav band of all tme Metallica. this pwns. i love me some neversoft.