I’m less pessimistic. Microsoft has engineers with a business mindset in charge. For now, it’s true. But we saw node vs IO.js — Microsoft can’t afford a fork or they lose their own control. They won’t close open source, they’ll add subscription or cloud usage fees for large enterprises. The value, like GNU “open core” is that open is popular, while enterprise features on the other hand are expensive. The enterprise is being led now by open source because it’s cheap, then value add to solve the problems they still have around control and oversight, etc.

If anything, I expect basic Visual Studio internals will eventually get open sourced as cheaper to maintain that way than Roslyn rebuild-all-the-things. And VS Code will adopt them and continue to cannibalize VS mindshare.