pregnant routeNow that their kink is mostly fleshed out there isn't much left to do story wise besides finding new places/people and ways to screw. I think that's why the last scene had the NTR twist to try to add some 'spice' I guess and give some excuses for adding other kinks maybe like BDSM etc and also possibly open the door to actual NTR for other paths/endings.
I think it's the road block most games of this genre run into. Once the 'slow burn' or corruption is done and the main part of the story progresses there isn't much you can actually do with the couple. Either they separate because things went bad or they keep going which just means new scenarios for them to screw which is where we find ourselves now. Most NTR/NTS games don't have a plot or story since the NTR/NTS IS the story and people just seem to enjoy the corruption and depravity which generally puts a cap on creativity.
I think wrapping up this game and starting a new one with similar themes but an actual story is probably the devs best move.