Nice move if what they want is for all of Grooveshark users worldwide start downloading music again when they manage to shut it down.
From my understanding (could be wrong) the label's aren't getting paid for their music through Grooveshark, so if they're not getting paid they'd likely prefer to force users to jump through the hoops of pirating music then from using a service such as Grooveshark. (actually they'd prefer you use a free service like Spotify which pays for the music rights).
What I'm saying is that they would benefit a lot more from having Grooveshark as an ally (even if not entirely on their terms) then defeating it and getting back to square zero in the anti-piracy effort.