I would have ended the 7th book differently. I would have had Albus send his parents an owl the next day, saying, "Father, please don't be mad at me. The Sorting Hat gave me a choice, just as it did you. I chose Slytherin, because when we were riding on Hogwarts Express, a creepy girl named Dolores Enigma was on there (name sound familiar?). She had platinum blonde hair and blue eyes, and she reminded me of a cross between an angora cat and a ravenous lion. She was sorted into Gryffindor; that's why I chose Slytherin. As it is, I'm going to be keeping a sharp eye out for James."
If J.K. Rowling got enough clamor regarding this hanging ending, she may choose to continue the series at a later date.