In a year's time there is no Little Richard DLC, with the keyboard that would be great. Little Richard's piano riff wooo would be the best DLC song ever! 
In all seriousness I would actually really love it if they put out some classical/jazz piano in as DLC.
Don't say  "but it's called Rockband" because there is country music and some hip hop DLC already in it.
Maybe some moonlight sonata, maybe some more Elton John. I think  that would be great. 
I just hope the keyboard will open up some music like that to be in the game.