1up is reporting on a rumor that seems to have some weight to it suggesting that the controllers for Rock Band and Guitar Hero III will NOT be cross compatible. If this is the case it means gamers will either have to fork over more then the cost of a Wii for both bundles.

From the article:
‘Harmonix develops and bases all of our games, guitars and other peripherals on open standards established by platform manufacturers such as Microsoft and Sony. Rock Band is no exception and supports an open controller standard,’ said a Harmonix spokesperson. ‘Guitar controllers are like any other standard game controller — -the controller sends a signal back to the game depending on the buttons you push. If a third party game controller is based on open standards, then it should work with Rock Band as well.’

This would suggest that Guitar Hero III’s interface doesn’t use the open standards provided by Microsoft and Sony. The conspiracy theory would suggest Guitar Hero III purposely implements a closed controller standard so it can only properly interface with the peripherals specifically designed for it. That makes sense, as Rock Band is the biggest competition Guitar Hero faces this holiday season and purposely locking out a rival’s peripheral directly forces consumers to choose one or the other — a convenient option given that Guitar Hero III ships ahead of Rock Band.