That doesn't make a whole lot of sense. If what you said is true, then that means when Canon does a rebate, less people will buy the camera as the price will be more. Therefore, Canon would anticipate overall less sales with the rebate. So if that was true, then Canon would deter potential sales by releasing the rebate. Why would they want to halt sales?
In the worst case scenario, they (being the retailers) keep the price the same and simply keep the entire rebate for themselves. But it makes no sense whatsoever that they would RAISE the price, because they'll be shooting themselves in the foot.
since its been happening for a couple of years now, and Canon cameras fly out the door, your assumption of fewer sales isn't valid.
Most cameras are sold at big box stores like best buy, and buyers see rebate and hurry to get one before it ends. Another factor is that the camera retailer must give the rebate at the time of sale, and later file a application for a refund or credit for the money they advanced. They don't like this, and just bumping the price $100 or $200 eliminates the drain on cash flow.
Last fall, on the day the rebates came out, I checked the web site of a large retailer, and while I was viewing it, the price of the 7D jumped $200.