Actually, if anything I have noticed the prices are creeping up already. So if you are going to buy one cheap, now would probably be the time. For the next few months they will probably go back up to normal prices. Good luck.
Prices after Christmas tend to vary a lot, it all depends on the item you're looking at.
If it's a really popular item, chances are they over-stocked on them, and thought they would sell them all before Christmas. After Christmas, some stores will have temporary large discounts on popular items after Christmas to return the stock to its normal state.
On the other hand, the price of less popular, and more obscure items tend to go up, most likely so they can compensate for those over-stocked items.