The show has been put on hiatus for marketing reasons.
It seems that Community can't even get a proper burial. NBC announced yesterday that it was indefinitely delaying the release of Community as well as Whitney, the show proving that Hollywood is creatively bankrupt. The reason? NBC wants to ensure that the shows get properly marketed, something they've been unable to do due to the surprising success of The Voice and Revolution.
According to a statement released by NBC, the network proclaimed that "given the success we’ve had for the past four weeks – including winning the first week of the season in A18-49 — we’ve decided to continue to concentrate our promotional strength on our new NBC shows that are scheduled Monday through Wednesday and have therefore decided to hold Community and Whitney from their previously announced premieres of October 19th." Delaying Community will allow them to focus on shows that still have a shot at gaining new viewers, something that neither Community nor Whitney is likely to do.
NBC should be announcing new premiere dates sometime in the not too distant future. Whether they push the shows to November or hold them until January remains to be seen. In the meantime, NBC will show Grimm reruns during the Friday evening timeslot.