Welcome to INTERCOT!
They do sometimes have December deals although they are never guaranteed. Here's information on historic discount offers
You can go ahead and book now though and still get the discount applied once it is released. I would recommend booking through our sponsor, Magical Journeys
. They'll keep an eye out for discounts that pertain to you and automatically apply them to your reservation when they are released with no additional effort on your part. There is also no additional cost to use them (they are paid by Disney), and they are fabulous to work with.