Imagine the most requested band on the forums to appear on release date with (as mentioned above) the epic "Butterlies & Hurricanes" an other songs. THAT would be a very clever move.
And again: If you are a developer and have a huge community asking for a specific band that has gained a lot of fans over the past 5 years AND YOU CANNOT bring them into the game you would be frustrated - and not making fun of the guys in the community.
HMX knows about their keyboard-plans for at least... say 2 years. They saved MUSE for RB3 DLC. Trust me! Let guitar hero have a fake Matt Bellamy - we will get the whole MUSE awesomeness.
P.S.: English is not my first language.