Eh. It is vast, but the tide is shifting. Non-UI components were never that good. WPF is in maintenance mode. And there is a growing need for deep learning which is currently a total lackluster in .NET

Still, more likely to be Python and C++ than Rust.

See ONYX, DirectML and ML.NET announcements at BUILD.

Python and C++ aren't replacements for C# due to different issues with them (which are not present in Rust).

Neither ONNX, nor DirectML, nor ML.NET excel at deep learning. TorchSharp is the closest to what is needed for the modern ML work, and there is almost no investment in it - I believe there's just one person working on it, and even that is part time.

The only thing that keeps me on C# is lack of Rust debuggers that would be able to evaluate arbitrary Rust expressions including full support for traits.