They do, but not adding features to please us language geeks, rather what makes sense to interop with .NET libraries, CLS compliant.

Roslyn for VB.NET still gets more love than F# across .NET workloads.

Now it is true that they could rename CLR into C# Language Runtime, given the extent of effort that C# gets, versus VB.NET, F# and C++/CLI.

Isn't the Roslyn compiler open source? It might be possible to maintain a fork and bring the language to parity with upcoming C#/.NET features.