It's a tough spot to be in. AMD and Intel split the largest chunk of the cake because their products are cheap, so they make money in volume.

The only reason nvidia has 20% of the GPU market at all is because their products are better, but without volume, there is very little separating you from losing the market.

If NVIDIA slips over AMD and Intel perf wise during one generation, the competition will have cheaper and better products, so it's pretty much game over.