He doesn't require any poll to add whatever content to his own game but i do believe that he said it for a reason that he considers the Twins line done unless the patrons want otherwise. In my eyes this translates as follows: He has no intention to continue with them but is open to do so if thats what patrons want, in poll fashion. If they want the family members mostly, all the time, he will no doubt add more than just the family members still but won't continue with the Twins in such case. It would mean Celia, Judy, classmates, Aunty, Violet. But the twins are done.
Even if not and he changes his mind (which he can obviously) i highly doubt that the story will take a grim turn and my view on the matter is that some people take the Twins questline way too seriously. Expecting dire consquences. This isn't DoD or DA, Icstor's games were always light hearted porn games. I'm expecting this one to remain true to this tradition.