I just got off the phone making a reservation a while ago and had a very chatty CM. I asked if he knew what this was about and he said it's supposed to be a variety of things. Everything from info re: the Fantasyland Expansion (things that hadn't previously been announced/released) to some major promo. He said they weren't given many details other than beginning January 1st, it's going to be very busy for them. He said they're not normally given that kind of warning of how busy it's going to get unless it's something very big like free dining,
but he doesn't know exactly what it will be, just that it will be BIG. Now, I know hearing this from a phone reservationist CM may be along the same lines of "hearing it from the bus driver", but he sounded pretty certain. We shall see!