I think so, but we're talking chronological release and not using terms such as "prequel".
Also, Guitar Hero III is definitely coming to PS2, and also 360 (since it got II). I bet a PS3 version comes out too. But they said they're not abandoning PS2. Think how many people bought the guitars, so late in the PS2 lifespan. Think how many people own PS2s. There is still money to be made.
The questionable thing is how the new development team will fare at making a worthy sequel.