Here is an interview done by PCGames with Ed Beach (whom we all know and love) and Dennis Shirk (Lead Producer): https://www.pcgamesn.com/civilization-vi/civ-6-gathering-storm-natural-disasters If you scroll about halfway down they ask Shirk about the Black Plague scenario that will be included and if disease mechanics will make their way into the full game. His reply is: "No, no. We didn't want to have disease YET." Later on in that reply he mentions that they sometimes use scenarios as a place to test out ideas they will put into the game. Now this is basically conjecture on my part, but there are two tiny hints at it in that reply. What do you guys think? I don't remember there ever being a 3rd expansion for a Civ game before so I still very much doubt it, but it's not impossible.