This feels like a potentially missed opportunity to add mirroring features to Pagure. Git has excellent support for mirroring, and if a bare repo is used (no locally checked-out branch) the mirrors can be maintained in a totally automated fashion.
(A post I wrote @ the GitLab community detailing how I’ve accidentally been maintaining local mirrors of three GitHub projects, because I set it up in a cron job on my account as a proof-of-concept, forgot about it, and it’s been steadily updating every 15 minutes for the past (now) three years. Never once failed or had the slightest hiccup. The only issue I hit was the logs growing too quickly, until I removed some verbosity.)
There’s no reason (other than the lack of an implementation) the team shouldn’t be able to migrate their repos to GitLab, get all of the features they want out of hosting their projects there, but still have the old Pagure repos continue to stay up to date with the latest commits. It’d be like they never left, at least from a source-code perspective.