Wouldn’t Civ6 be the first game in a long time without a spin-off to utilize the existing game engine? Civ4 had ‘Colonization 2’. Civ5 had ‘Beyond Earth’. (Was there actually a spin-off of Civ3? I never played it and therefore didn’t pay attention.) I still believe we will get a new game using Civ6’s engine before Civ7 will launch.