I don't see Nvidia losing any market share unless AMD has a better performing GPU than Nvidia once all the chips fall. If my guess is wrong in my last post and Nvidia does hold off on the GP100 for consumer cards (even though they are the first chips they are making) until Q1'17, there will be quite a few hold outs that will wait and see which is the better card (look at the recent 980ti/Fury releases for a recent example of plenty of hold outs until both cards were out where in Q2'15 the market sales of cards dropped to the lowest level in 10 years, and in Q3 the sales rebounded 9%... basically most people waited to purchase a card even though they could have gotten a 980ti in Q2'15, they waited to see what the Fury was going to do performance wise, and then bought their cards in Q3 instead).
But I don't see Nvidia sitting on their high end card (for which they are already making the GPU for use in HPC/enterprise cards) if AMD has a card that can significantly outperform whatever Nvidia's top consumer card on the market at that time. Nvidia's game is to maximize profits on their entire product line, which means only releasing something when there is a compelling MARKET reason to release it (in other words a competing product is on the market or extremely close to being on the market, or declining sales on existing products due to product stagnation).
You may also be right that Nvidia may lose some market share, but their numbers can really only go down anyway: