The F# ecosystem probably would not survive abandonment by Microsoft. F# the language would probably be fine, but without the .NET runtime and tooling, it probably wouldn't be compelling. It is not widely adopted in industry, so I think finding corporate sponsorship sufficient to keep it up at the level of the other languages is slim. I don't imagine a world where there is enough community support to keep it relevant.
F# has been a first-class language in .NET for at least 15 years and has lived on under Ballmer and Satya. It seems to serve as a useful R&D program for both the runtime's capabilities and for features that may go into C#, which will be the premiere language barring a cataclysm. I don't think it's quite as precarious as it might seem on the surface.
I don't think C# is going to be dropped in the foreseeable future. I don't really think F# will be either, for the reasons I just articulated, but the thought is experiment is "can F# survive if Microsoft drops it."
F# has been a first-class language in .NET for at least 15 years and has lived on under Ballmer and Satya. It seems to serve as a useful R&D program for both the runtime's capabilities and for features that may go into C#, which will be the premiere language barring a cataclysm. I don't think it's quite as precarious as it might seem on the surface.