Above anything else, I would love to see F# get more love. From my experience, it's in a weird place where .NET devs would love to use it, but either don't see the benefit of switching, or don't see how to switch.

If Microsoft were to tackle a new language, I'd love to see a systems language, especially as many industries still use Windows to build software in C++. A language that can be used alongside Rust for things like gaming would be fantastic.