I think your being to much of a chicken little.
Yes micron drops are slowing. But did you know the Geforce gtx 680 was the first Nvidia card on 28nm. The jump from the 680 to the 980ti is nothing short of amazing. You'd go from 35fps in battlefield to 78 at 1440p . Its the same generation micron node.
So for instance MS would be able to release a console next year taking advantage of 14nm and then a year or two down the line release a gpu for it that takes advantage of a new design giving much better performance.
Or MS can put out a Zen plus GCN and sell it as a system. But oh you want xbox vr ? Well here is a second GCN to keep performance the same in all games with the vr helmet
http://www.anandtech.com/show/10133/amd-xconnect-external-radeons
View attachment 1202
Or hey ... Want that awesome surface pro but also want to game. Here you go
View attachment 1203
The trick would be the price premium. I would imagine MS wouldn't want you to be able to upgrade the xbox except with a specific card.
But the tech is there. Heck if the casing sans graphics card was a $100 I would buy it if I had a laptop or tablet it worked with. I would then put my old card in there when my main rig got updated
So now we have the radeon rx 480 that is $200 or $230 (?) for the 4/8 gig. Its 5.5tflops of power uses less than a 150w.
We have the current rumor of a xbox one scorpio launching next year at 6tflops or greater. I can still see them creating an enclosure above using a radeon rx 480 and using it for vr modes where each gpu renders an eye.