Harry Potter 8th book (who knows)

In an interview Rowling gave us clues that she could, who knows, write an 8th book.
Rowling confirmed that there isn't a university after Hogwarts and further Harry Potter books.
Q: Do you think that you will write about Harry after he graduates from Hogwarts? Isn't there a University of Wizardry?A: There's no University for Wizards. At the moment I'm only planning to write seven Harry Potter books. I won't say "never," but I have no plans to write an eighth book.