Monday night Nightly News showed a brief shot of the now-dismantled Studio 3C and I was able to figure out how much the floor plan I posted earlier differs from the present day setup. The red line I added below is the wall of 3C that had the window looking out over the newsroom.
Now here's where it gets interesting. The large storage room to the left of 3C on the floorplan is believed to be the old Studio 3H. Studio 3H was the first studio in 30 Rock to be converted for TV use, all the way back in 1935, and the only TV studio in 30 Rock until the late 1940's.
I have to question how much larger they'll be able to make the studio, as there appears to be structural support columns in the wall shared with 3H. Unless they are planning on undertaking a massive overhaul of the building's frame, they'll end up with a situation like WABC, with large poles in the middle of the studio, meaning they'll either need manually-operated cameras or partially-robotic cameras.