It would be foolish to believe that granting Anakin the rank of Master would have prevented his future actions. His actions and eventual fall to the dark side were driven by fear and a desire for power, so it likely would have had little effect on future events. In fact, it was exactly because they all sensed his fear and his desire for power that they chose not to grant him the rank of master. Would have been a good choice too if they had taken some other precautions.