I've been a full-time GPU engineer at a couple of major companies for about 6 years now. My colleagues at my current company have all been GPU engineers (and video, prior to that) in the 20--30 year range.
While a lot of the technical details are correct, there are a lot of red-flags in this guy's essay. For instance:
> Although AMD and NV have the resources to do it, the smaller IHVs (Intel, PowerVR, Qualcomm, etc)
Intel owns, what? 60? 70 percent of the desktop market? More? PVR, Qualcomm, etc. own 90% of the mobile market? Intel has an enormous number of GPU engineers---far more than AMD, and easily comparable to (or more than) NV.
Now, to OP's statement about DX12 & Metal: obviously they were developed cojointly with AAA game developers. The major title developers are in constant contact with every major IHV and OS vendor (less so for open-source) at all stages with respect to driver- and API- development.
Furthermore, it's not like the major architects and engineers of these driver teams are total tools; these guys live and breathe GPU architecture (and uarch), and are intimately familiar with what would make a good driver.
The impetus for these low level APIs is differentiation and performance. When those couldn't be had from GPU HW, the next place to look is "one up the stack": driver & API. It surprised no one in the industry that Mantle/Vulkan/Metal/DX12 all came out at about the same time: we've all been pushing for this for years.
There's several parts to this. DirectX 12 is going to run on Windows 10, and its adoption by developers is probably going to be entirely driven by how much of their target audience can be persuaded to upgrade from Windows 7. If Windows ships with better DirectX 12 drivers than Vulkan drivers (and I would bet that it will), then you'll probably see more AAA games written to DirectX12. Metal, likewise, is the preferred graphics API for reaching iPhone users, which are plentiful and (compared to Android users) lucrative.