Every fall, dates move, and every fall the comments decide it means a film is in trouble. Sometimes it is. Often it is just the calendar getting crowded, a format window opening up, or a marketing plan that needs more runway.
My general read after a few years covering this: a move to a quieter weekend is often confidence, a move deep into winter with no explanation is the one to watch, and a move off the calendar entirely is where the worry is justified.