Not much more to say than that, really. To adjust for Community's return, NBC has pushed 30 Rock to 8:30, and Parks And Recreation will take a break from airing new shows until Up All Night has finished its first season on the same night.
No word on NBC's reasoning for bringing the show back now, but considering the brouhaha surrounding this season of the show, it's hard not to imagine that these episodes will likely be the last ones that Community airs. We'll know if it gets a fourth season sometime in the next few months, but it seems...unlikely, to say the least. Enjoy the show while it lasts, in other words!