My best guess is there will be a modes based around making the game as difficult as possible. Removing AI trading, when you friend the AI it kills you city states, any cheese they can think of. If they put a lifetime mechanic on units and increase maintenance after promotions it would make warmongering harder. Drifting continents: Start a Pangea then the land splits into continents, then splits into islands? Atlantis Mode: Your island starts with a volcano and you must get off before it explodes and sinks the whole island. Voice of the people mode: Like city state quests but you start to loose loyalty the longer you don't complete it. Alien invasion? Dragon attack?