7970's would be one of the worst cards to buy purely for mining as well... if you're going to game with it also, sure.
Otherwise you're purchasing a card that's going to decline in value (absolute $) more than any other card out there over the next few months
Are you jusy saying that because of the 8*** series cards coming out or?
newer technology always declines in value faster
if the next series comes out, then the effect would be even more pronounced
right now you can buy a 7850 or 7870 and if you do the rebate and sell the games, then you could already sell the card used and make a profit on it (actually, i suppose the card would still be "new")