"HMX is committed to establishing Rock Band as a platform," reads a forum post from representative HMXHenry. We'd like to encourage the interoperability of instruments between platforms so that players can experience music, and our games, with their instrument of choice."
It was not specified if Rock Band instruments will be usable in the impending Guitar Hero World Tour, due October 26 with 86 on-disc tracks, which adds drums and vocals to the traditionally guitar-only franchise. The instruments for both games will be cross-compatible in the PlayStation 3 and Xbox 360 releases.
Likewise, it is unclear if Guitar Hero World Tour's Wii guitars and drums will be compatible with Rock Band 2, though it is likely that the new guitars will function in Rock Band 2 as they can also be used for the already-released Guitar Hero 3.
However, both games are confirmed to sport support for downloadable songs for Wii--a much-requested feature found in previous non-Wii editions of both franchises--with Harmonix having just announced that all existing and future Rock Band DLC will be brought to the Wii through weekly releases, beginning with 30 songs at launch.