In contrary to T.R. Knight's case, Katherine Heigl is looking forward to return to "Grey's Anatomy". The actress' character, Izzie, had a flat line at the end of season 5 but sources have been saying that Heigl has made a decision to "come back", meaning Izzie may escape death.
Izzie, portrayed in the whole season suffering from stadium IV brain and liver cancer, had a complex surgery which turned out successful. However, she later endured complications from the cancer treatment and drifted off from the voice of her friends who were trying to save her. At the same time, Knight's character George O'Malley was struggling to survive from a massive trauma due to bus accident.
ABC still remains mum about the casting news, mostly due to its relationship with the cliffhanger. When the sixth season debuts this Fall, the fate of both Izzie and George will be determined. Katherine Heigl herself has publicly declared her willingness to continue with the role.
In the meantime, news are busting that Knight's request for contract termination has been approved by the studio. He reportedly wants to pursue other things outside "Grey's Anatomy" because the show did not provide a good storyline for his character.