Typically, we do see lower prices in December for Canon products. This is because Canon's fiscal year ends December 31. Thats when the profit / loss and sales figures that go into their annual report are determined.
In order to make things look as good as possible, Canon reduces prices to clear out inventory. This year, there is a world wide financial crisis and sales are poor. The poor sales and the end of year will result in some really big discounts, but they will be of the form of one or two day blowout sales rather than a price drop.
Just be ready to jump on one when it comes. For example, I see a new 5D MK III for $USD 2799 on ebay this morning. its likely a one day only sale.
-1....Canon doesn't build finish goods then stock them in warehouse. Canon will build your 5D III based on dealer orders(qty). It calls build-to-order or FIFO.
It's all about lean, cost reduction and floor space.