So if you've read one book, you can no longer read another book in your mind? If you play one game, you can never play another game in your mind? Your only hope is that the creator will endlessly add to that existing content?
You have a completed story with what currently exists. Separating into a sequel does no harm to this existing story. Yet, if you continue, you risk the code getting unwieldy. Things like branches that never panned out don't have to be carried forward into the new game, where as its unnecessary code slop if you continue forward and thus leads to dev cycles taking longer. You're being stupid and promoting an idea that doesn't benefit you, does nothing to protect the existing content, and only makes the code work more difficult moving forward. Look at basically any other AVN out there, they do what I suggested. Oh, and that's before considering things like future remasters and things like that.
No, these characters stories aren't done being told. I'm saying to separate the story arcs as you would see in a manga/anime instead of generic seasons. The next arc of this story is going to be much more difficult to pull off. It's likely going to be significantly longer bc the problem is systemic and not some ground level grunts perving.