People need to do some research. They release DLC every so often, but we have no clue what's coming now. Nowhere has it said the whole discography is on.
From what I read, they have access to the whole discography, but they have to do the charting in the UK so it is much more expensive overall.
In other words, if the DLC isn't selling much better than regular, I wouldn't expect a whole lot more out of TB:RB.