Rock Band, is currently in a standoff against Warner Music Group. Apparently MTV has been unable to produce a single new licensing deal, since WMG CEO Edgar Bronfman decided last August that the company deserves higher rates from rhythm games. Both sides are currently willing to wait this out, so don't expect any artists from WMG to show up as Rock Band DLC once the present deals conclude -- allegedly this summer.
It's not exactly clear where Activision Blizzard, publishers of the Guitar Hero franchise, stand in this battle royal(ties). Actilizzard CEO Bobby Kotick was very vocal late last year when Bronfman started whining about licensing fees, going so far as to say that perhaps music companies should pay game publishers to feature their tracks in games.
[Via The Cut Scene]