And what would have happend with the discrete graphics performance in that "change to another paradigm"? It's not like their development will stop or halt.
Have you tried gaming on integrated graphics? Integrated is just not close to the performance of discrete graphics.
Also, I am strongly inclined to agree with the person you quoted about paradigms; I believe in a few years, though it's impossible to know for sure, that the dGPU market will be dead except the high-end market. Though high-margin, it is a very low-volume segment of the industry for gamers, professionals, and those simply who want the latest and greatest. We've already reached the point where the low-end dGPU market has been all but destroyed by Intel and AMD's steady march toward serviceable iGPUs, and if the rumors and roadmaps are to be believed (and again, they may not come true), the mid-end will be decimated in a few years simply because the performance will be good and acceptable, eliminating the need for a separate GPU for most users. The high-end will likely exist for years to come, but I could even theoretically see a future where super-high end graphics are merged with the CPU as well, but now we're just speculating with no basis for reality.
It's important to remember that what we perceive as fixed now is itself only a nascent at best. The entire computer industry as we know it has only existed for a few decades and is constantly in flux as far as paradigms. That's why the forward thinking generally succeed (but sometimes fail, if they're too far ahead of their time). To expect our current model of modular motherboards and add-on cards to continue in its current form forever is misguided. Just look at network cards and sound cards. The same could theoretically happen to the GPU industry. It may not, but I think it's more likely than not.