Exactly. A big concern for enterprise customers (that often drove them to Atlassian over Github) was the fear that Github was "just a startup" and might disappear at any moment and the lack of integration with existing enterprise tools. If MS can put together a comprehensive platform here that doesn't cost an arm and a leg they could dominate this market.
The real story here is that nobody wants to host their own services and nobody wants to spend time/money even integrating various hosted solutions. The success of Atlassian and this acquisition confirms that people want to pay a flat monthly fee and get access to a bunch of highly integrated, quality services. The web continues to drive the creation of highly centralized platforms (Amazon, Facebook, Google) and it doesn't look like IT development market is going to be any different.
That's a fair point in that I was unaware they had IPOed as many years back as they had (I had thought it more recent). It was partly a joke. But I have worked with people of a Fortune Xty company mindset that didn't consider vendors unless they were also Fortune Xty +/- Y companies, and yet some of them used Atlassian products despite being outside their usual Y margin, which I found fascinating.
Those enterprise customers are probably already using Visual Studio Online, which already gives you the best of both worlds - Git for source control, superb backlog and CI/CD features, and ADFS authentication.
IMO, for private repos, VSO is far superior to GitHub.
Having MS backing GitHub suddenly makes it a feasible option for a lot of conservative enterprise customers.