I think PBR may be ending this story but he is considering (hopefully) a sequel set in this world. He has some really good ideas for directions to take it. Plus I hope in a sequel he could clean some of the more deviant themes (not judging just couldn't figure out a better description) and move out of the high school setting, letting him put the new game on steam so he could make some bank.
Part of the allure of this setting is that all the characters are all bad people in some way. Yes, I know its a porn game, but PBR throws some pretty good literary chops if you look beyond the surface. Its a good exploration of human corruption in variety of different forms. Each character is corrupted in a different way for different reasons. I think its a pretty cool and unique story.
Id love to see GG is a different setting, I always kind of looked at her like a porno Walter White. Its a great story where you take a good, sympathetic character and then completely corrupt them, making them the ultimate villain. Id love this arc for GG and seeing how far she can go being completely without boundaries of morality, and not in just a sexual way.
Yes, it is going to have a bad ending, but I think we have a long way to climb before a really, really epic, Macbeth type fall.