The worst case scenario with Github closing the door, assuming no heads up, is that you'd lose your issues and PR. You have your git history on a bunch of machines (your devs + you should really have a dedicated backup).
The worst case scenario with Microsoft having visibility of your "closed" source code is that they take a peek at it and implement a better faster more integrated version of them in their own product competing with you, or heck even copy/paste your code. What can you do about it? How could you prove it? Remember, they can afford orders of magnitude more number of lawyer hours than you.
https://en.wikipedia.org/wiki/SCO%E2%80%93Linux_disputes#Mic...
Github was losing money, but that's pretty typical for SaaS businesses. I have no reason to think they couldn't have gotten to break-even. And if the can't get to break even, I have no reason to think Microsoft will subsidize them indefinitely.
I use Bit Bucket because I knew they were making money and were solvent and I knew GitHub was just waiting for a big pay day. BOY was I wrong with the timing and the amount.
> And if the can't get to break even, I have no reason to think Microsoft will subsidize them indefinitely.
This fits perfectly with their developer system with Virtual Studio, VS Code and Azure. I can't see how this isn't a great buy for them and their ecco-system.
All it takes is one rogue employee, and it could have devastating irreversible effects on a small startup.
https://en.wikipedia.org/wiki/J%C3%A9r%C3%B4me_Kerviel#Unaut...
Of course, Microsoft was famous for their dirty pool tactics in the past, so it's not irrational to worry that they'd return to them. E.g.: https://en.wikipedia.org/wiki/Microsoft_litigation#Private
I would argue that the case here is quite the opposite.
Github is loved for a variety of reasons, small & large decisions that are influenced by how profit-oriented the company is. And how willing they are to annoy their users to squeeze some more "profit" and/or data out of them.