Yeah...like others have said, it may be possible -- depending on the school. Some won't accept scores later than the October dates AT ALL and some will only accept them as a re-take. I was stuck in a position where I had no choice but to take the PCAT in January this year, and although things turned out ok in the end, it was a lot more stress than it was worth. I would have paid $1,000 (maybe even 2K!) to take the earlier test if I could have -- unfortunately by the time I realized I could apply to schools this year it was already too late. I had to rely on a loophole of it not being required if you have a BS in order to even be considered at one school. Some others put my application on hold until receiving scores. You don't want to be in the situation where you could possibly be rejected because the class is already full when you might have been accepted at an earlier point in the admissions cycle.
Why do you want to wait until January?