This whole discussion just made me laugh whilst remembering the hype around the Transmeta / Torvalds code-morphing engine.
Ah, the 90's. They were fun.
CPUs have been "general purpose" since day one. The only non-general purpose hardware are ASICs (like the article says). Everything else is just marketing hype from Intel, et al.
This is such an amazing rehash of what Intel used to call *T technologies in the 90's, starting from the 80's, when coprocessors started appearing (x87). The big trend was toward DSPs in the 90's, but that never happened, instead they pushed on new hardware like MMX, SSE and now vector processors. That's why we have graphics processors as non-general-purpose CPUs.
To call something a GPGPU is just an egregious assault of on common sense.
"Dark silicon", while a catchy name, is simply a side effect of latency, something the article mostly skips (hints at it with locality): the memory hierarchy exists and dark silicon is a result. When latency is zero, more of the silicon will be engaged.
While one could easily claim that because parts of any chip power down that means it's not general purpose, that's an oversimplification: 100% utilization is fundamentally impossible because problems aren't solved that way, there is no infinite parallelism.
I really think the author's analysis isn't fully developed. While the conclusion that hardware looks like the software may be a pleasant tautology, it overlooks Turing's thesis entirely. Which is odd, because that's what they author -started- with!