I've been lacking on this post since I went on Vacation last month. I never wanted to catch up on everything, and didn't want to nec jump back in, but I think jumping back in wins.
I see one mention of christmas going back to yesterday (unless I'm ninja-ed by the time I post this) but not much more than it's listenable and playable (not how you get it)
This article says that the entire christmas album will be unlockable content in the game, and also mentioned info on how the photos are unlocked (each song has 2, one at 3*s and 1 at 5*), and the tutorials (45 vox ones, 86 drumming ones). Some of the other stuff may have been mentioned, didn't see it in the main post that I could tell.