Wow, this is an old topic!
I doubt Rowling will kill off Ron . . . Ron is Harry's sidekick. She'd want to make him last until the seventh book, because he's really the comic relief of the series. Without Ron, the series would be so depressing that they'd be almost impossible to read. I mean, think about it . . . if only Harry and Hermione remained, can't you imagine how glum things would be? They would be worrying all the time . . . and Harry would go crazy . . . not a very pretty picture!
It's a fascinating possibility, but I hope it doesn't come to pass, because Ron's one of my favorite characters.