I'd love to see The Cabal on Mars, but there aren't anymore commanding officers from their army in the system right now, so they'd have to send more Cabal in. If they decide they want to attack us, then I'd be really excited to see a raid on Earth. It'd be crazy to see the Cabal there, and the sort of terrain we would be fighting on would be pretty cool depending on where they strike at (close to the Traveler I'd assume).