F# was originally just kind of a passion project that MS insisted get productized to continue development. It's still very much an internal favorite within Microsoft Research and the Bing team, from my understanding.
Don is still working on F#. The F# team at MS now is bigger than is was years ago. People from different companies and the community are collaborating on compiler and language features.
F# is beyond microsoft, a lot of early adopters are still there.
