The problem is that state franchising laws make it almost impossible for GM to close divisions. Their legal obligations to their dealers make this prohibitively expensive. It cost billions to close down Olds and they don't have the money anymore. This will only happen if GM declares Chapter 11 which will void their dealer contracts.
I believe that we could see GM go into Chapter 11 bankruptcy in order to totally revamp its finances and re-emerge as a much more streamlined company selling vehicles that people really want.