That's an interesting point. From my perspective one of the main arguments for Windows continuation as the PC gaming platform is backwards compatibility with older games, but if Linux is beginning to eclipse it in that regard it's lost one of its biggest bargaining chips. I think game devs really need to start moving away from DirectX-only support, though I dare say many of those decisions are inflicted on them by publishers after getting a cosy deal with MS...
It's actually been like that for a while already. I.e. Linux+Wine being able to run older Windows games better than latest Windows can.
And regarding developers. Vulkan really started moving things forward, and now with Stadia more developers will get familiar with it. So that will further erode DirectX-only mindset.
