I think it's an exaggeration to say "it doesn't look pretty for Microsoft" especially since the drop in C# can be explained in part by Microsoft actively encouraging C# devs to start writing TypeScript/JavaScript applications. Microsoft has decided the future is TypeScript. If you want C# on mobile your best bet is to look at Xamarin, which is run by Miguel de Icaza of Mono fame. I'm curious how much MS has invested in that company.

Reference: https://www.youtube.com/watch?v=3-5nExkCvAY