For those curious, the federation roadmap is here: https://codeberg.org/forgejo-contrib/federation/src/branch/m...
I'm watching this pretty closely, I've been mirroring my GitHub repos to my own forgejo instance for a few weeks, but am waiting for more federation before I reverse the mirrors.
Also will plug this tool for configuring mirrors: https://github.com/PatNei/GITHUB2FORGEJO
Note that Forgejo's API has a bug right now and you need to manually re-configure the mirror credentials for the mirrors to continue to receive updates.