Twenty years after the day the threat of the hell goddess had been ended Xander and Cordelia still watched over their territory, Sunnydale. They and Dawn were the only Scoobies left. Oz had died in a plane crash eight years ago. Joyce died two years ago, a grandmother to Dawn's three girls Anna, Christie and Carmen. Giles and Jenny had been killed by demons trying to open the Hellmouth ten years ago. Buffy and Faith had died within a year of each other fifteen years ago, themselves. Faith's death calling a new Slayer, that never came to the Hellmouth. Willow and Tara, who adopted a young girl who's parents were victims of vampires, died protecting her from a crazy human who thought she was an alien. Xander and Cordelia took the girl, Suzie, in and raised her along with their two sons, Mark and Sam. Amy went out stopping another witch from trying to kill people for a ritual she was doing. Connie continued to offer counseling to both the Scooby Gang and victims until her retirement and return to England, she carefully chose a replacement therapist to bring into the fold, before leaving.
Heidi eventually recovered enough to leave the long term mental health facility and earned her diploma. She never came back to Sunnydale, but did stay in touch with Xander and Cordelia. Kyle remained in the care facility for the rest of his life. Rhonda eventually succeeded in relearning everything she'd forgotten and she too, graduated from High School and then college becoming an advocate for abused children.
Xander and Cordelia discovered another aspect of their hybridism, one that also affected their children, they aged more slowly. At forty, they barely looked more then twenty five. They would continue to age at a much slower rate until they died in their mid eighties, looking twenty years younger. They had turned the guardianship of their territory over to their children, who passed down the guarding of Sunnydale far into the future.