T.R. Knight, Jessica Capshaw and Katherine Heigl T.R. Knight, Jessica Capshaw and Katherine Heigl

With the Grey's Anatomy writing staff due back to work next week, hard decisions are starting to be made about who will and won't be walking the halls of Seattle Grace this fall. And thus far, we have at least one "casualty."

T.R. Knight made his last appearance as George in the show's shocking season finale in May, and will not be back in the fall, EW.com reports.

Knight's exit, unconfirmed by either ABC or his personal rep, suggests that George will not survive the severe trauma he suffered in the end-of-season bus accident. Grey's creator Shonda Rhimes recently dismissed the idea of giving the character an "extreme makeover" and recasting with a new actor as "ridiculous."

The good news is that Jessica Capshaw will not only return to Grey's this season, but she has also been promoted to series regular status, sources tell TVGuide.com.

Capshaw's Dr. Arizona Robbins arrived midway through last season and quickly established herself as a fan favorite, as the quirky, perky head of pediatric surgery struck a spark with Sara Ramirez's bi-curious Callie.

Now all eyes are on Katherine Heigl. The season finale also placed a sizable question mark on the fate of Izzie, who rebounded — only to then suffer an abrupt setback — following brain tumor surgery.

Although Heigl has not been lacking for big-screen roles, she said in March that should Rhimes want to keep Izzie alive, "I'm there." Can Grey's possibly weather the loss of two original cast members in one fell swoop?

An ABC spokesperson would not discuss Heigl's contract status, while the actress' personal rep did not immediately respond to a request for comment.