I'm not so sure the Ultra will drive the price of the GTX down appreciably. NVidia's target market for this card is mostly high-end niche builders like Falcon, Alienware, Polywell, etc and geeks w/lots of disposable income.
I think the card's going to retail considerably higher than the current GTX's pricing...so why would the price of the GTX come down? This is all conjecture on my part...my gut feeling, if you will.
Now, I hope the price of the GTX DOES come down; I want one, but not at anything over $400.
But w/ATI floundering in the water and out of the high-end graphics game for the forseeable future, why should NVidia lower any prices at all?