Not going to dispute your points above simply because I consider it an educated guess at best to predict the future and 5 years is a long time in tech, however it doesn't change my position that I will buy Nvidia if their product is better than the AMD alternative and vice versa but I'm not going to crusade for AMD and buy their stuff just to try and balance the market share if the kit is not up to scratch.
I always buy legitimate hardware from legitimate companies, if I don't have the money I don't buy it.
Would also like to add that lets say more people buy AMD products just to try and keep them alive and to stop a monopoly and they succeed to the degree that AMD don't go under but are still behind both in Processors and GFX cards say for the next 3-5 years, who are the ones to benefit? Not the AMD crusaders as they will still be buying the potentially inferior components regardless of how they have affected Nvidia and Intels market share and product releases, those buying Nvidia and Intel would stand to gain the most as Nvidia and Intel would potentially be releasing the superior hardware at more competitive prices to continue to compete.
I get that it's an unorthodox way of looking at it and of course AMD could up their game but it's still a valid point and I certainly wouldn't want to have been buying the inferior tech just to reach the same point in 3 years time and say why did I do that.