Question about J.K.Rowling?

I think any more Harry Potter books might very well ruin the stories, however I think it would be really neat if she used the same world of wizards to write another story or series set elsewhere, such as here in the states, with completely different characters and little, if any, mention of Hogwarts and all that. Maybe show how the world really is with a dark wizard or witch in complete control, just not Voldemort.