I would expect, if supplies last till Christmas, some crazy Black Friday and Cyber Monday deals on 7970s. Right now you can buy them new for under $300, god only knows what sort of fire sale we might see on a few lucky selections.
Dual GPU vs Single GPU, two different markets. Also, the 290X is the "new" card, thus it will have a higher price.
If last year's Black Friday/Cyber Monday deals were of any indication, I highly doubt the 7970 would receive that much of a price cut on those sales days. Amazon/Newegg/NCIX/TigerDirect were pretty much only severely discounting the low end spectrum of cards, not the high end.
One can always hope though!