They've already given the show a full episode order for S1, so why would a hiatus prompt them to cancel it?
History has shown (NBC's own history, mind you) that first year shows with a long hiatus do not return with a resurgence of viewers. The show is in its first season, and is still finding an audience. This isn't Season 3 of Lost, where viewership is so high that viewers will come back no matter what; its a brand new show.
This show will likely be cancelled at the end of Season 1 if viewers do not return in the Spring.