It's on Ausiello's Q &A:
Question: Some very mean and nasty people have been saying that Sandra Oh is leaving Grey's Anatomy, whenever it comes back. Since you are the god of TV scoop, I knew you'd be able to deny this for me.— BrittenayOh, Grey's Anatomy returns this Thursday for it's final episode (strike casualty). Bailey is narrating this one and we're made to prepare for something emotional. When the show went on Christmas break, they left us with a part one of Crash Into Me.. My guess is, Bailey's sacrifices at work will take a toll on her marriage, and she will lose either her husband or her son.
Ausiello: Interesting. Unfortunately, I can't verify that rumor's authenticity. What I can verify is that someone — and a major someone at that — wants to be discharged from Seattle Grace, and STAT. But, as far as I can tell, that someone is not Sandra Oh.