Sandra Oh's contract on Grey's Anatomy expires at the end of season 8 and there's no official word yet on whether she'll sign on for another season or not. So far we know that Sandra has other projects in development, but it all still remains hush-hush.
Sandra's colleague Kevin McKidd was asked about their contract status on Grey's on Twitter yesterday, and if his gut feeling is correct, Sandra Oh will be around for season 9:
Earlier this fall, Sandra's other co-star, Ellen Pompeo, has discussed the possibility of a Grey's Anatomy without Cristina Yang. Read more about that here