Do you think it would be possible for there to be some Beatles side projects as DLC? I would love to see some Wings songs, or John Lennon solo material on the store.

I'm sure Harmonix will be focusing on The Beatles as a group, so unless they somehow run out of Beatles songs to release, I'll be very surprised to see solo projects thrown in.

As much as I would like to see All Things Must Pass as DLC, the licensing would be a nightmare.  

Dhani Harrison mentioned the possibility of solo work as DLC in some interview, though I think he may have just been saying something like "it would be cool", not "it will happen". 
 
I'd sure as hell buy a lot of it....well, maybe not Ringo's. I'd pay entirely too much money for George's "All Things Must Pass" album though.

There are too many Beatles songs that aren't in the game for that to be a realistic situation.

I would love The Travelling Wilburys on rock band, doesn't even need to be beatles rock band, just to have some songs from them would be awesome.