6C was vacant the last time I was in 30 Rock, a year or so ago. It was being used as WNBC(TV) master control, and as an emergency studio for WNBC. A corner of it was also being used as master control for WPXN before Pax/i moved out of the building.
I think pretty much everything that had been on 3 has been reconfigured into the new NBC News/MSNBC newsroom/studio complex. I expect it'll be unrecognizable next time I'm through there.