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.

So long as it's not a total bore for the rest of the band, I'm all for it :)

there are songs out there with nothing but vocals and guitar.  I could see songs with only one instrument.  Going forward, I think Rock Band is going to get smarter and smarter.  It will star to realize the group of people you are playing with... what instruments are active, what genre's you've been selecting frequently, and it will suggest songs for you.
 
Seriously.  I have some great ideas if Harmonix wanted to hire me...  :)  Like that will happen.

Elton John? Maybe. Moonlight Sonata? I wouldn't hold your breath.

Moonlight Sonata? What the fuck are you on?

" Moonlight Sonata? What the fuck are you on? "

Billy Joel is a great start. Elton John definitely deserves a similar treatment. Tiny Dancer is a must. Let's not deny this fact.

I would like to see some Elton John too. Though I'd dare anyone to sing Goodbye Yellow Brick Road on expert perfectly. Fucking hard.

What it really needs is some Ray Charles

They held off on releasing Bill Bruford's Earthworks - "Footloose & Fancy Free" on Rock Band Network presumably for this reason! I'd better get it when RBN 2.0 comes out next year >:( 
 
  

Now they have a keyboard Pendulum songs can be in the mix, and THAT will be awesome.

I'm still standing Ya Ya Ya! 

" So long as it's not a total bore for the rest of the band, I'm all for it :) "