At the moment, nobody knows for sure. It was originally slated for release in July, then the publishers pushed it back till the autumn; now The Independent reports that it might not even be published till June 2003! So I'm afraid you'll just have to sit tight for the moment. But I'm sure that when a firm date is set, the details won't be hard to find!
I'll quote a recent article by J.K Rowling. She said that although she has completed a good portion of the book she still needs to complete a lot more.
Maybe J.K Rowling is gonna write Harry Potter six and keep it to herself so that no one else will be able to read it.......don't listen to me.....I'm an Idiot!