I'm not sure that the data really supports this, though.
The low-end of the dGPU market is obviously going away/pretty much gone, but I think the dGPU for gamers and professionals will continue to thrive for a good long while.
What this will probably translate into, though, is higher prices for mid-range and high-end discrete chips to offset the loss of the low-end volumes. Fortunately, this is a market where people have shown that they are willing to pay for performance, and hardware requirements for games are continually rising.
That's a dead-end game. The money needed to design and construct those high-end GPUs is a product of economies of scale. At its heart a 980 Ti GPU is essentially still a Maxwell design, which was intro'd with the 970/980/750/750Ti.
What you're saying is like saying Cadillac would be just fine if GMC / Chevy / Buick went away, not realizing that a Cadillac engine is nothing more than a tweaked Chevy engine.
For perspective, if you total up the Steam HW survey quantity of 970s, 960s, 750, and 750Ti - it comes up to 9.07%.
The 980 by comparison has 0.99%. The 980 Ti and Titan don't even rank, meaning below 0.3%.
If we start looking at mobile dGPUs as well - the 840M is the highest with 1.3%. That means there are at least 4x more 840Ms out there than 980 Ti's. *at least*
So basically you are talking about 98% of Nvidia's unit sales in the 970 and below category + mobile. Without those sales, Nvidia would have to stop R&D.
But the iGPU is a long ways off from matching up against ~$100 dGPUs. A GTX 740 or 750 will blow them out of the water. That'll change but we're not there yet. The only time I see favorable comparisons for iGPUs is with odd graphics settings vs some crap dGPU like an r7 240 DDR3.