J.K. Rowling, who read a selection from Sorceror’s Stone at the annual White House Easter Egg Roll, responded to a question about future novels with this:
“I’m quite sure in the not-too-distant future, I will bring out another book.”
The vagueness of her response is fairly telling. Rowling didn’t specify if said “book” would take place in the Harry Potter universe or not. My guess is it won’t.
Would I be opposed to a Harry Potter novel that takes place with a grown-up Harry and Ron as Aurors? Absolutely not.