I am a devoted reader and admirer of J.K. Rowling, and it honestly pains me a bit to say this, but from a literary perspective, she's out of control here. Her abundant generosity with information is surely a response to a vast, insatiable fan base that does not have a high tolerance for never-ending suspense, ambiguity or nuance.
It would also be understandable if, after more than a decade of telling stories about this world and these characters, Rowling is unable to stop. She has been a great and comprehensive builder of a fictional universe, and she's famous for keeping reams of folders containing the back stories and astrological signs of every major and minor character ever to appear in her pages. One of the things that made the Potter books so good was the sense that Rowling had utter mastery over every corner of her realm. Who could blame her for wanting to keep the kids happy by doling out bits of it? It's not as though Rowling would be setting a precedent: J.R.R. Tolkien spent much of his post-Middle-earth life tinkering with the details of the world he created, and delighting and gratifying his adherents by providing them with additional information about it.
But when too much of the back story (and, more disconcertingly, the future story) gets revealed –- especially in an age in which an author is not simply sending letters to readers as Tolkien did, but making utterances that will be disseminated and analyzed by a global network of Web sites -- it seems to have not so much a gratifying effect as a deadening one.
I suppose it's nice to know that in Rowling's mind, Harry is a successful auror. But in my mind, based on the seven books I devoured, Harry, whose greatest gifts were as a teacher, is the Defense Against the Dark Arts professor and eventually the Hogwarts headmaster. I suppose in the minds of other readers, Harry might manage a Quidditch team, or work for his uncle Vernon at Grunnings or something. I'd love to have that conversation with those other readers; I'd also love to have it with Rowling, in a Tolkien-style exchange. But when Rowling declares to an international audience what Harry's adult job is, then the possibility for such an exchange is over. Speculation over what Rowling might have wanted us to surmise about her hero's future is over. Bully for Harry, boo for the notion that fictional characters take on lives of their own in their readers' minds.