Honestly, I hope she doesn't write any more of them.
I LOVED the series, but I think everything that needs to be resolved has been resolved, and the series has ended exactly as it should. THere's nothing more that needs to really be done to expand on Harry's story.
However, if more books are to be written taking place in the world of Harry Potter, there are some things that could be pretty interesting. A Chronicle of the founders of Hogwarts could be pretty cool. I'd love to hear book 7 told from the inside of hogwarts, showing us what went on with Luna, Neville, and all of them. And finally, I'd love to read a book that follows Luna in her no doubt adventurous life after book 7. She was always one of my favorite characters, and I was dissappointed that she was neglected in the end of book 7.