Of course, by this point, Jon (who was in Sarah's 25-year old body) wasn't even himself anymore. All of the wishing that had been done had changed his mind too much. And the same had happened to Sarah.
Jon loved being in Sarah's body. He never wanted to swap back. And neither did Sarah, who was fine with being a crossdressing guy, whether she was role-playing or not.
Both Jon and Sarah became sexually excited in anticipation for what was coming next.