I agree with others - just keep trying, someone may cancel. I booked our vacation just two weeks ago and we're going the same time as the OP Dec.15-21. We got ADR's at Crystal Palace, Sci Fi, Coral Reef, Boma for dinner and breakfast, and then several days after we booked, I was able to get Cinderella's Royal Table for lunch!
I'm still trying for 'Ohana, but if we don't get it, no big deal, we're already using more TS credits than what we get with FD. Two years ago we ate at 'Ohana and I know I didn't book that more than two months out.