...and she might kill off Harry for good measure. She's been saying so for quite a while. Her new reason is a good one: she won't be tempted to bring him back if he's dead. (Apparently, no one has told Rowling about the return of Sherlock Holmes after he was killed -- and that was in a world that didn't even include magic.) Rowling drew gasps a few years ago at a reading of (I think) Book Five when kids were allowed to ask questions and one tot wondered if Harry might become a teacher at Hogwarts after he graduated. Rowling responded with, Well, you're assuming that Harry's going to live. causing a frenzy of delicious despair.
SPOILER IF YOU HAVEN'T READ THE BOOKS
Obviously, killing Dumbledore in Book Six (assuming he WAS killed) was a strong step to take. But it would only be the death of Ron or Hermione that would really count as a "kill." Hagrid would be too easy a tearjerker, Snape giving his life to protect Harry too obvious, bringing back Dumbledore so he could die again (remember, he went over the side of the castle tower rather than dying in front of our eyes and we never saw the body until it was in a coffin) too cheap, etc. What made the most sense after Book Five was having Neville Longbottom die to save Harry, but since they ignored his character in Book Six, that seems less likely. Still, Neville dying for Harry or Snape dying for Harry seem the most likely to me, with Ron buying it as well for good measure.