It helps that now most (if not all) parts of the stack are open source and run on Linux.
I might be biased from having worked with production F#, but it feels more like functional is making its way into C#, as the general industry sees value in functional principles. So F# feels like its more here to stay?
C# still doesn't see itself as a functional programming language, even as it has added so many features. It may never get first-class currying or the broader ideas like generalized computation expressions, for instance. It certainly won't get F#'s cleaner syntax with fewer mandatory semicolons and whitespace nesting rather than curly brackets.
F# probably isn't going to disappear for a lot of similar reasons that GHC (the Glasgow Haskell Compiler) didn't disappear when F# was started (nor when key contributors left Microsoft). F# often already sees more outside open source contributors than contributions from Microsoft employees.