7970 isn't going to reduce 670 prices, its more like the other way around.
AMD need to make a card with out of the box performance equal to a GTX 680 to equally compete and steal any thunder, and yet they are taking a very long time to do that.
That doesn't really make sense, nvidea can raise price at the minute while demand exceeds supply but as soon as new tech comes out with higher or equal specs they'll have no option but to lower prices to undercut the new amd cards just as the 680 undercut amd on launch