That might change with WSL drastically increasing the demand for such a thing. With enough resources, doing it as an X server is the better approach because it gives more flexibility - top-level windows can be shown directly on the host desktop etc. And with enough demand, there are resources for something like X410...
I've used both Xrdp and X410 for my WSL UI needs, and so far X140 has been a much better experience by far.
In terms of sheer number of active users, yeah, I'm fairly sure it is. There's lots and lots of developers who live in the Microsoft bubble, who might have never even heard of Cygwin - but who will hear about WSL from their routine conferences, training etc.
If anything the amount to choose from went down not up, slowly replaced by RDP clients.
So that tells who will will win.