I don't see that relantionship with fuckboi lasting that much.And i think that him supporting her doing the sex scene will start the destruction of their relantionship.
I think is very hard to predict how this gonna end.I think he'll forgive but getting back together is another whole story.And the doesn't see to reedem her so much.
I think the reunion with the 4 major characters for a final conflict would have more impact.And them make another impactful moment beetwen Sakura and Shinobu for their final conversation.