Gringott's Vault

yeah, it's true, j.k. rowling might write an other book..but it won't be about harry potter..it'll be about the magic world, a kind of encyclopaedia as she said..so, don't expect she'll carry on with harry or his sons and so on..but i think if she write it it'll be fun..oh, she wanted to do it for charity, i've heard..well, it's a good thing..

here's what it's written about this book on her official website:

"Will you write more Harry Potter books after the seventh?

If you mean more novels, then I think it highly unlikely. I’ve got enough story for seven books and I never planned to carry the story beyond the end of book seven. I might do an eighth book for charity, a kind of encyclopaedia of the world so that I could use all the extra material that’s not in the books... we’ll see!"

and here's the link where you might find something more:

http://www.jkrowling.com/textonly/en/faq_view.cfm?id=24