Shonda said more than once that Izzie's won't get a brain tumor! And Katherine also said that she has no intention to leave the show. So I'm really not worried about the Ausiello spoiler. Sometimes he has fun to exaggerate things.
And I can remember that he was also wrong in the past. Remember the Callie storyline and that she is pregnant? That was from Ausiello, and it was wrong. So we shouldn't believe anything what he says.
The only thing that is for sure is that JDM will be back and that Hahn discovers a connection between one of her patients and one of her residents. I think that's Izzie. It's rumored that it's the patient from season 2 who didn't get the heart because Izzie tricked Hahn.