So we'll have a house of kings campaign since their Kell, Prime, and Archon are all active. Being the Kings their bosses should be a step above the Wolves or other lesser houses. The Cabal should be reinforcing Mars soon in preparation for clearing the rest of the system, their main fleet elements will have troop types we haven't seen yet, Naval Troopers, etc The vex information network was mapped by Dr. Shim's team, we have data monsters and dangerous thought constructs to fight there. Rasputin is seemingly standing off with the city, if he gained control of a faction of Exos or a golden age drone army, he could represent a huge threat, trying to wipe out organic life to save digital life from the darkness. Those are just off the top of my head.