There is a sync function between relays being built called stir fry. I am starting to tinker with this. I imagine a large portion of the best relays will sync together and will be the most generic. No porn and decent moderation. Then there will be other pockets of relays syncing together that allow a free for all. No restrictions. It will be up to the clients on what relays they allow users to add. Clients are easy to build so there will always be one able to access the moderated content.

As the eco system evolved there will be ways to filter content so that only post from paid relays show up in the feed and other cool settings.