They've had this for a while now and is one of the main reasons I ended up using GitLab for some of my side projects. I don't think this is going away I think it's just another part of their business model.
It is, our on-premises income is more than enough to pay for GitLab.com. We might introduce more paid plans in the future but I don't expect you'll ever have to pay for the things we offer for free now.
We run GitLab.com so we have a reference for a very large GitLab instance that is in heavy use. We do offer paid support for it, but there is also a public, free support forum.