People saying that it is easy to migrate don’t know what they are talking about. GitHub isn’t just Git hosting, but a social network of open source developers and projects. You can’t migrate stars, issues with comments and the history of PRs, all linked to the profiles of their authors.
And sure you can self-host GitLab, I pushed for it at my previous employer and works great for on premises deployments, but it’s not the same for OSS if the community you care about isn’t there.
That said I am glad to see Nat Friedman as the new CEO. This gives me some hope for its future.