Aside from the special-editions of Guitar Hero III, the true successor will have some funky new additions including custom song creation and support for multiple instruments, reports C3 News.
Guitar Hero IV, due for release this fall, is said to include drum and vocal work (much like EA's Rock Band effort), alongside the expected Bass and Guitar. [Will they then change the name of the game? We also hear that Gibson is working on their own alternative to Guitar Hero and Rock Band. It rumored be a package that includes a real guitar and a real amp, but you'll have to come up with the music on your own.] - more on this story