[I have an actual update post, but that'll be tomorrow, as I'm just online fleetingly before going to bed. I saw this on a quick glance at LJ and had to post, though.]
Edit: On reflection . . .
Her "I would have told you earlier if I knew it would make you so happy." rang somewhat false to me because she's aware enough of what's going on in fandom to know that much of fandom is pro-gay. This article says of the interview: "Oh, my god," Rowling, 42, concluded with a laugh, "the fan fiction". *rolls eyes*
There are plenty of posts about how the Dumbledore reveal is problematic in a Celluloid Closet kind of way -- he had one great love, who went evil and he had to kill him, he then appears to be celibate for the rest of his life and doesn't live to the end of the series. As I read and discuss and suss out, I find that what I keep coming back to is that out of all the Hogwarts students we get to know or who get mentioned in passing, none ever mention a same-sex crush or are mentioned as having a same-sex girlfriend or boyfriend. (I'm willing to give more of a pass for the adult characters, since we don't hear much about romantic partnerships of any of the adults who aren't parents -- though the Yule Ball surely could have included a line about some Professor dancing with his/her same-sex spouse.) If she really is so blasé about gayness, did she really only have one character out of how many scores of characters in mind as gay?
Anyway, other stuff:
fox11013 has thoughtful thoughts on "what this is going to do to people recounting the history of anything and everything in children's and YA literature " -- among other topics.
executrix comments: "Hey, maybe now JKR will do Director's Cuts of the books, and defining HP canon will be like trying to decide whether to do Folio or Quarto Lear, or some conflation of the two."
The nice theory is that stating DD's sexuality just didn't fit. You couldn't do it too early (like with Doge), because it revealed too much about the Grindelwald plotline. You couldn't do it through Skeeter, because to do it in character would make the accusation of homosexuality look like it was icky and bad. Kings' Cross would have been... well, the whole thing was focused more on Harry. There might have been spots to put it in, but would it have completely jerked non-slash fans out of the narrative? Very likely.marauderthesn suggests ways the Dumbledore=>Grindelwald subtext could have been made text in a way which would have fit the book.
Edit 2: Leaky Cauldron transcript