Call me crazy, but I think that it's premature to think that Microsoft's days of bungling acquisitions are over. They probably will manage to ruin Github, the catch being that it'll happen over a much longer timescale.

Really should have seen that when Atom fell to the sidelines in favor of VS Code.

Admittedly though, I don't see myself using Gitlab anytime soon, if not indefinitely. What makes Github special, arguably, is that it looks less "businessy" and more fun and social.

Another reason why I think the ruination of Github will happen over a longer timescale. Any competitors will likely try to focus on trying to be different (i.e. Gitlab's focus on open source and dev ops) rather than try to focus on on what made Github special and do it better than Microsoft could ever hope to do.

EDIT: just to clarify, this comment relates because forcing teams to use products developed in-house erodes team culture. It's an attempt at assimilation.