I agree with what you are saying. However, I do believe that it is POSSIBLE that the death of Eunice and the knowledge of her years of prayer for him could have resulted in a true conversion of the heart.
He was pro abortion to his last breath. There was no evidence, other than this letter to the Pope (which contains no acknowledgment of his debauchery) that he had any conversion to Christ. If anything he was simply trying to convince himself that he was WORTHY of heaven because he took so many dollars from people who worked and gave them to his political allies.
Ted Kennedy's legacy will be that he did for America what he did for Mary Jo Kopechne. He drove the ship of state off a bridge and then left the scene to let us drown.