I go every year on the week after Xmas and all except this past year was COOOOLD!
2002-03 shocked me, though. It was very warm, 70s, until about the 3rd of January. Then it went to the 50s in the heat of the day.
I always expect the Christmas crowd to disappear after New Years day but I learned not to expect that this year also. Since the New Year's day was on a Weds this year, people and the crowds remained until the weekend. I'd expect the same this year also since New Years day in on a Thurs this time.
Despite the inconsistency, it is my favorite time of year in Orlando. I prefer cold weather and prefer it over the sweltering heat Orlando is known for. I also love the decorations and the atmosphere, which is most of the reason why I like being there then.
HTH!