Scholastic CEO, Richard Robinson, was interviewed by NYTimes and hinted that there would be future Rowling books. When questioned about the future of Scholastic without Potter, Robinson replied “We can believe this is the last book on Harry Potter.” In following up on that the Times asked whether Scholastic had first option on any other series. Robinson answered that Scholastic is loyal to Rowling and she to them and that it is “less likely we won’t get it [future book]. It’s more likley it won’t be another Harry Potter.”
It would be interesting to see what Rowling can come up with after Harry Potter. It’s a big lighting bolt to fill but if anyone can do it, surely it’s the creator herself.