Well, I'm not quite familiar with Canadian Currency, but right now you can get the Geforce 7800 GTX for as low as $525 US off of Newegg.
The Geforce 7800 GT is rumored to come priced at around $449 US dollars. But following the trend of the GTX, in the first couple months, prices could decrease to potentially in the $300 range.
I foresee the 6800 GT Dropping in price, but closer to when the full lineup of the Ge 7000 series is actually introduced, which I expect to be sometime close to the release of ATI's r520.
I would also bet we see the 7800 GTX fall in price, again, near the release of the r520, simply due to competition. How low it would drop may depend on cost of the competiting card. Ultimately, though, I wouldn't be surprised if when that happens, we could see prices as low as $499. Heck, I've even seen people say they've already gotten in that low with coupons and such.
The best thing to do is probably just wait, but if that's not an option, then you could be shooting yourself in the foot if prices were to see a somewhat drop.