Looks Like It's OfficialThanks to Kotaku for a link to this Boston Globe story:
Activision spokeswoman Maryanne Lataif said her company was willing to work with Harmonix to make the various game controllers fully compatible with one another. "Unfortunately for Rock Band users, Harmonix has been unwilling to discuss an agreement that will allow us to provide that option in a manner that maintains the high standards people have come to expect from Activision," Lataif said.
She added that any agreement will involve someone at Harmonix writing a check. "We believe we should be compensated for the use of our technology," said Lataif.
I can cut through all that in one word: L-O-S-E-R.