Time for the alternative theory.
Yes, we are getting "closer" to the release of a 5D MkIII, but we are getting "closer" to every event in the future, including the end of the world. No one outside of Canon knows how much closer we are getting.
People assume that the recent price drops are related to a planned release of a new model. But, there are many other possible explanations.
The price drops do seem to have at least tacit approval from Canon, since they don't seem to be enforcing the standard minimum pricing requirements that usually go with their rebates. However, note that this is the same with their lenses and other DSLR models as well. The 70-200 mm f2.8 IS II has shown a price drop that is as dramatic as the 5D. Does that mean they are replacing the 70-200mm lens?
Retailers drop prices at Christmas time in order to capture as many consumer dollars as they can. Besides the competition between one another, they know this is the time of year when consumers are at their lowest resistance level and a "bargain" can easily push a consumer to buy a little more than he or she planned to. Once the wallet is open, it is much easier to snag a few more dollars out of it.
2011 has been a tough year for businesses all around. Whether it's a major retailer or a supplier like Canon, they are eying their year-end sales numbers and want to end with a strong performance in the fourth quarter. As long as the volume makes up for the reduced margin, trading margins for volume can help their bottom line.
Finally, I keep reminding every one that price cuts can just as easily mean a supplier does not have new product in the wings. Imagine for a minute that Canon knows they won't have a 5D MkIII ready for another nine to 12 months. Armed with that knowledge, what would you do? I know I would shave prices as much as possible in order to grab market share now. 5D buyers are not making one-time purchases and ultimately, I know that if they have my camera, they will be buying my lenses and if they have my lenses, they will be buying my camera bodies in the future.
So, what's the best strategy? Reduce prices on my top consumer model and my top selling luxury lens. Sell the 70-200 f2.8 II to current owners of 5Ds and 7Ds to lock them in. Sell 5Ds to current owners of 7Ds and other APS-C upgraders. With every 5D II or 70-200 f2.8 they sell, they know they locked in a permanent customer who has no real choice to but to wait as long as it takes for the replacement model to come out.
Now, I'm not pretending to have any real knowledge of Canon's strategy and it's entirely possible we could see a 5D MkIII announced tomorrow (doubt it), I'm just suggesting that no one should assume that current pricing strategies are driven solely by a development schedule.
I know I've gotten seriously off track from the original post. But, here is what I would suggest you consider: We are seeing a "perfect storm" of low prices right now. They may go lower. But they may go higher. It's always a gamble. Buy when the price is right for you.