Not on its own. There's such a gulf in price currently between the 1070 and 1080 that they can easily drop the price of the 1080 and maintain a reasonable gap between the two cards.Do you reckon it'll effect the 1070 market at all?
That said, if Vega releases around then, I reckon they're going to gun for the 1070 with the smaller Vega and will attempt to outperform or undercut it(or both). This could necessitate a price cut in and of itself.
A larger Vega could similarly try and do the same to the GTX1080, which would be another reason to suspect a price cut for it is likely.