We can't see the future — we can't even really see the past, not the way you are asking. This is one of the trickiest things: what you're asking is, essentially, a complex counterfactual along the lines of, "if nuclear weapons didn't exist, what would the world look like in terms of wars?"

Given that nuclear weapons do and did exist, and were a major part of the context of the world post-1945, it's pretty impossible to know with any certainty what it would be like if they didn't. Maybe everything would be totally the same, more or less. Maybe it'd be totally different. Maybe it'd be something in between those poles! Maybe it'd be more like 1914-1945. Maybe it'd be more like 1870-1914? Maybe it'd be its own thing!? You can see how there are really lots and lots of possibilities here.

And it's also worth keeping in mind that we don't even really know how much nuclear weapons played a role in making the world after 1945 the way it is, as opposed to other things. The legacy of World War II would still have been there without the nukes, and it's a big legacy! The United Nations would have been still created — maybe that by itself would have changed things? And so on and so on.

Now, the tricky thing here is that we can say, with some confidence, "the period from 1914-1945 was characterized by a couple GIANT wars that had GIANT casualties, and the period from 1945-present was instead characterized by MANY small-medium sized wars that still had a lot of casualties, but no GIANT wars." And people who want to argue in favor of nuclear weapons tend to say, "see! That's the effect of nukes — it prevents GIANT wars (and shuffles that aggression into smaller wars, and coups, and revolutions, and so on). And that's WAY BETTER because GIANT wars are the worst." So there are political stakes to that question.

In opposition to this, you have people who point out as I did that it's very hard to "measure" the effect of nukes versus other things, and it's also not an obvious thing that the "many smaller wars" is the better outcome except when measured as a rough fraction of global population killed in wars (which goes down... but also during the post-1945, the global population shoots way up for reasons having nothing to do with nukes — and more to do with food and health and industrialization — and so that dramatically "dilutes" deaths from wars anyway). Many of those "smaller wars" still killed millions of people; there are a significant number of scholars who have started to object that the Cold War wasn't all that "Cold" in any objective sense, it was only "Cold" in the sense that "it could have hypothetically been a lot hotter."

Anyway, I'm giving you a non-answer that is really just meant to sketch the dimensions of possible answers one could give, which is usually the best you can truthfully do for these kinds of massive hypotheticals. I do think it is interesting that most people take all of this for granted, and don't realize how difficult it is to actually prove or demonstrate these things.