I see this trend accelerating so for once it seems Microsoft has read the tea leaves correctly.
In comparison to say WPF, the web stack was very lacking. It wasn't for example until a few years ago that we got CSS grids. Heck, HTML components are still not mainstream, despite solving a very problem... which doesn't elsewhere.
https://visualstudiomagazine.com/articles/2019/09/26/blazor-...
Mono supports Windows Forms: https://www.mono-project.com/docs/gui/winforms/
Still rough around the edges, but it's coming together.
Mono's implementation no longer works on newest versions of macOS unless you compile it and a bunch of other stuff yourself.
So no its not really coming together.
With the current state of the tech it would be Qt (very awkward for the web though, using WASM?), or a modern web framwework with a design framework (e.g. Angular + Material Design) inside native wrappers. I don't see how MS could step in with some silver bullet solution.
I'm just not sure x-plat desktop is a place where MS needed to step in to fill the void.