Adapt http://mirrors.opensuse.org to list the new release
Adapt the mirrorbrain "markers" and the index header template to list which mirrors provide the new release
Template file is
Lars mentioned that there might be a problem with status of mirroring in case that there would be a parallel release of a large maintenance update (libreoffice etc). It would be nice to give a heads up to mirror admins (firstname.lastname@example.org) to sync it ahead of the time.