Rock Band timed Xbox 360 exclusive?

On his blog Game/Life Chris Kohler has been speculating for the past few days that Rock Band could become a timed Xbox 360 exclusive. At first, he had no evidence but relied on the fact that the PS2 timed exclusive of Guitar Hero 2 didn't impact the sales of the Xbox 360 version of the game. Next, he had a scan of the invite he was sent for the Rock Band E3 event which had an Xbox 360 logo but lacked one for the PS3. Now, he found in last night's PS3 price drop press sheet there was a list of the major third party releases for the PS3... and Rock Band wasn't on the list. Now this could just be a coincidence, but I think he may be on to something. Sony doesn't have the install base to support such an expensive game and since timed releases haven't hurt Harmonix in the past, why should they be worried now?

I'm very curious to see if he is right on this one.