Based on last year, there's a good chance that something will be offered for December stays. Here's what was offered last year (2006), and it looks like the discounts came out in August for December stays:
Check ins between 10/1/06-12/23/06 package discounts for Disney Rewards Visa cardholders became available on 8/14/06, exp 9/30/06
Check ins between 10/1/06-12/23/06 Annual Passholder room-only rates became available on 8/16/06, exp 12/23/06
Check ins between 10/1/06-12/23/06 Florida resident room-only rates became available on 8/16/06, exp 12/23/06
Check ins between 10/1/06-12/23/06 package discounts for general public became available on 8/17/06, exp 9/30/06
Check ins between 10/30/06-12/23/06 "available to anyone" room-only code became available on 9/28/06, exp 10/29/06
Check ins between 11/1/06-12/23/06 package discounts for general public became available on 10/2/06, exp 10/31/06
I have made reservations ahead of time and then switched when deals came out with no problems before (they just credited my credit card) BUT it all depends on availability at the time of booking, etc. You might want to have a second resort choice ready just in case availability was not at your first choice when they would go in to switch your ressie over to a deal. I would be sure and jump as soon as I saw my dates come up to help guarantee getting the resort you want!
Keep watching mousesavers.com and here on the DIS for news of deals!
