Like others, I missed it after I finished the last book. Every so often I wonder about an expanded universe, but I think most of the questions or issues I have are so minor that Rowling could have, and possibly has already, answered them in an interview somewhere and I'd be happy with that. Plus the ending was worthwhile enough that I don't think it needs to be milked. Things didn't finish out QUITE the way I expected, but it came close and I liked that.
All in all, though...it definitely doesn't need to be milked. People can speculate and fanrage or whatever all the want for all I care. It doesn't need anything else. We can only hope that everyone leaves it. Although I do fear that if anything, in about a decade, we'll get a prequel phenomenon like we did with Star Wars. Which....yeah. Really hoping that doesn't happen.