I have tent camped in mid December at Ft. Wilderness, and yes it gets cold, but I have a -20 sleeping bag and an electric blanket on my air mattress so once I get to bed I was pretty toasty.
The only problem is when you are in a hotel or RV, you can be warm without being in bed. Unless I was in bed, I was bundled up in my thermals, coat, hat, and gloves.
I'm hoping it goes back to a warm trend this December, plus I'm going earlier this year, Nov 29th - Dec 8th.
Carol