This play is so satirical that I'd definitely follow suit in your predictions. You can go anywhere with this........... does Jack continue to live a double life, maybe have another family? Is it possible to use this type of scenario to convey the same type of confusion in the future? Maybe the table gets turned, and someone finds something suspicious amongst Gwen's belongings; she of course in innocent, but reaction to the discovery could take you in many directions.
As far as Algernon and Cecily, I found Algernon to be quite the engaging character. He has a great sense of humor, and again you can turn the tables. Has the couple remained happy? Does Cecily go through her marriage looking for him to deceive her.......... maybe they have a son who plays the same game the two men have before him........... he disappears for years and sends a friend back in his place to woo and win the heart of Jack and Gwen's daughter............. everyone would be in a tizzy for nothing. Everything can come to light in the end........... 'boys will be boys."