One of the problems with band/musician content from previous games, is that they were rather limited and more "side content".
Bands (like in 2 and 3) were just four instruments that synch to play one of three looping tracks that sound similar to each other.
Singing (like in 1, 3 and 4), you had a number of different genres but with only one or two songs in each, so unless you wanted a variety performer, things got stale pretty fast.
Of course there are reasons for this, not only does each song have to be created from scratch, it has to sound good with different voices/instruments, and has to be made for different skill levels, the development work quickly multiplies.
So if they do a music pack, I hope it is much more central and focused. And instead of lots of genres with little depth, they go for a more narrow but deep focus.