If going by performance I'd project the following 'retail prices'
GTX 1180 $749
GTX 1170 $599
GTX 1160 $399
This gives just enough stratification to sell the cards but push down the older card prices only slightly.
Cut prices for old gen cards:
GTX 1080 TI $549 (when 1170 arrives)
GTX 1070 TI $349 (when 1160 arrives)
GTX 1060 $249
This is making performance assumptions that the GTX 1180 is significantly faster than 1080 Ti, that the 1170=1080 Ti, that the 1160>1070 Ti.
I think the 1160 will probably be in the 1070 Ti range of performance.
Things are about to get a lot more confusing as we see where these new GPUs actually slot in performance-wise and the price tags that Nvidia slaps on them.
I mean look at the 1180Ti. The 'retail' was $699 and it's still hovering around the $699-800 price point less than a month to release of the 1180.
I expect 1180 to be be in 1080ti range. Nvidia will have more shaders. I am not sure though If they can up the clocks too much. Had this been shrink to 7nm from 16nm. I would have expected 1180 to be much faster. Unless of course Nvidia found a magic pill and were able to up the clocks by 30-40% and shader count up by 30-40%. I would have expected both with 7nm. But going to 16 to 12 which is not actually as big as it looks. Not sure if they can do the same they did with pascal with minor shrink.