Adjusting for surviving birth, life expectancy varies wildly in both directions (although even considering that, "longer" is definitely less of a promise now than it has been for the last several decades).
I don't know if it's particularly optimistic - if you're (accurately) saying current life expectancy numbers don't take catastrophic risks into account, neither did calculations of life expectancy back then. Unless you think there is a higher risk of catastrophic events now than there was during the cold war.