Yeah, no dealer is going to make an offer like this without a fairly good degree of certainty that it's not going to pay off. If anything, they might have some better info that the next body to be announced is the 1D/s, in which case there'll be no 5D3 before next year.
The "99% probability" rumours of a 36MP Nikon D800 isn't going to help matters either (whether it turns out to be true or not, and whether canon will compete or not doesn't make much difference), people are still going to be in "wait-and-see" mode.
Kind of reminds me of when they replaced Wholesale Sales Tax in Australia with GST. Tax on cars was going down from 30% to 10%, so noone was buying cars in the months up to the switch, dealers had to drop the prices to post-gst levels to get people to keep buying cars to stay in business.
Same with the 5D2, I reckon people are finally starting to tail off with buying them, dealers are losing income, they have to give incentives to clear out their 5D2s before they're worth a lot less...