TVGuide pointed out:
Of course, if Rhimes is bundling the exit of Heigl and Knight as one rumor, it could be that just one of the actors (likely Heigl, whose film career is bustling) is actually booked for a goodbye, thus making it "not true."
It's amazing how one little word can make things!
I still think they'll both leave. TR hasn't been happy with his storylines in awhile (and honestly doesn't HAVE a storyline and hasn't since re-taking the test). Katherine has opened her mouth and complained a lot about the show's writers and how she feels her storylines are lackluster. Why would they want to keep her?
I can't say if I'll be sad or not if they leave -- I can say it'll be weird to have them gone, but sad? I don't know.