Just wanted to stop by to drop off the latest Writeup: the first one made based on a fan request, Hegemony, touches on all nine(?) species and their associated subspecies within the Covenant, and discusses their whereabouts and factional standings as of "present-day" Halo in 2558. It's pretty lengthy, but covers all bases save for the infinitesimally-known Covenant Fringe, so it's definitely worth a read if you're interested in where some of the various factions stand leading up to Halo 5: Guardians.