I don't think that's what OP meant; rather I read it literally, to mean one day there might actually be a world without war, or at least, a world without violent wars.
No they prevent and drastically reduce bloodshed.
Would Russia have spent the last 11 years attacking Ukraine if it were still a nuclear power?
(Maybe. Dictators are not reknowned for their sanity and good decision-making skills.)
If things go very wrong they have the potential to take us out. But a non-nuclear WWIII could, also--not by direct kills but by taking down the interconnected stuff that makes society work.
Also, while they serve to prevent direct wars between major powers they cause proxy wars between the major powers.