If he had remained in power, he would be the oldest head of state in the world.
Pahlavi was born in 1919 and was 60 when he died in 1980. Michael I of Romania was born in 1921 and was ousted by the Communists in 1947. He is not only the oldest surviving head of state from WWII, but is also the last surviving person to have held field marshal (five star equivalent) rank during the war.
The Shah would have died within two years - he had incurable cancer. His son would have been the new Shah. The son was western educated and would have been more liberal than his father had been - but still pro-American.