I've been to 343 a few times. They don't let anyone past the main foyer. There is a keycard locked door and all the Windows are blurred so you can't see inside the main workspace.
I've plotted an imaginary mission impossible style break in many many times...it's impenetrable man!!!
Guessing MS's holiday 2015 will be something like this:
September- Quantum Break
October- Forza 6, Gears Collection
November Halo 5, Rise of the Tomb Raider
Everything will be out by Black Friday imo.