PSA: You can (carefully) upgrade FreeIPA servers to Fedora 23 now

EDIT 2015-11-04: FreeIPA and pki-core that address the known upgrade bugs have now been pushed stable. It should now be OK to upgrade FreeIPA servers to Fedora 23, but I'd still advise you back the system up first, and check the package list from the upgrade carefully to make sure it's upgrading to the correct package versions.