It really depends on when the theater you're going to starts selling them. Some will sell sooner than others, some won't presell at all. It just depends.
When it gets closer to December call the theater and ask or keep an eye on
MovieTickets.com and the like.
Edit: Oh and as was said in your thread last night, you're still going to have to wait in a long line to get good seats on the first night unless you go to a theater with reserved seating.