There's very little stopping anyone from running their own Git server just like GitLab/GitHub did, if they're that concerned about it. I have one running for the companies' developers / collaborators and even one for my own personal projects and those that collaborate with me on those. Those are private, yes, but if I (or anyone) felt compelled to offer a GitHub alternative, then they can. No-one is forcing developers to use GitHub. I'm sure if there are enough concerns about policy changes, privacy, censorship, etc. then developers will migrate to other platforms ... just as they have for many years now. It's nothing new.
Don't like the new owners? Don't use it. Make one yourself. It's not rocket surgery.