Ben Carson
Mike Huckabee
Rick Santorum
Rick Perry
Mark Everson
Lindsey Graham
Carly Fiorina
Jeb Bush
Lincoln Chafee
... Were all born in the 1950's.
Kasich was also born in the 50s, and is more likely to be elected president that everyone on that list except Bush.
Several possible 2020 presidential candidates were born in the 50s: Susana Martinez, Mike Pence, and Rick Snyder if Clinton wins in 2016…or John Hickenlooper, Jay Nixon, and Deval Patrick, in the event that the Republican nominee wins in 2016.
You could also have a vice president born in the 50s take over in case something happens to the president. E.g., both Kaine and Warner were born in the 50s.
So there's still time. Someone born in 1959 will only be 61 years old at the time of the 2020 election, so it's not too late.