compatable and I assume you will be adding a quest system of some kind, and will you be adding more models?
Saves for Chapter 2 will always be compatible with new updates. A quest system will depend on your definition of it, if you are referring to the usual, do x, y and z , then buy something or fight someone, then no. I think in a game meant for faping it would be a bit boring (depends on the game though), so I will continue using the system I have right now where the "quests" are, go to the girl, talk to her and have her story develop a bit more or get some unique sex scenes, like Monika(Lana Rhoades) and Riley (Riley reed) yoga and sex session. Some of those unlock new characters or in some specific cases the possibility to impregnate some of the characters, so there is that.
I have several new characters, planed, some days my dick takes control and selects a lot of hot models for using in the game, then my other brain has to figure out where to put them. Just now I have a list of 50 models and only ten characters planed to go in the game. Since the next week in-game will not be like the third (first half of chapter 2) for reasons that are obvious if you played the game, there is a lot less room for adding characters, but Chapter 3 will be just open world with no "Main story", just a city for you to explore, and new stories with new and old girls to live through. It will be very easy to add new characters. When I decide that I will not add any more content to this game, it will be massive I assume (hopefully not much bigger then chapter 2 because it was already problematic to deal with it.)