Its difficult to say. Typically its a good time to go. Most schools are back from Christmas break, the holiday crowds have gone home. However, I've heard that a few schools are off until Jan 7. Which could bring in bigger then normal crowds that week.
The so. cal annual passholders can go back starting on the 2nd of January.. So we crowd the parks.. Also a lot of schools are off the 22nd- 8th. So I know I will be there with 10 other people...