Peace?
You mean there was no world war, but there were and are plenty of wars going on all the time. Also it is quite a risky bet, to assume all the actors will remain rational.
The only two actors capable of inflicting gigadeath are still the US and Russia. Both of them are ultimately run by oligarchs who want to remain alive, and have a population to lord over.
The actors who are genuinely irrational don't really have the number of nukes to do more than cause ~megadeath. This sort of thing would only happen once and then the actors would cease to exist.