A properly-designed computer-controlled flight system would do the same thing Captain Sullenberger did: evaluate landing options, choose the best one available, and ditch in the Hudson. "Properly designed" means the system would know which parts of the airplane were functioning at all times. In this case, that would mean it would plan a landing without adding any power. Guiding the airplane into the ditching would be no different than guiding it into any other landing.
I'm very skeptical that any such system will ever be deployed though.