What has changed? The situation today is much worse than it was in the 60's. We're still relatively antagonistic to several nuclear countries. Severely unstable countries (including former Soviet States) have nuclear stockpiles. Pakistan is nuclear with tremendous political corruption.

The chances of a conflict resulting in billions of deaths seems much higher today than it ever did.

Good points, but I personally feel safer in the present time, and even with global economic challenges, I feel generally optimistic about the current world situation. A economically and socially more tightly connected world seems more likely to be safe.

Chaos theory informs us that the future is impossible to predict for non trivial systems. I admit that I am partially relying on a gut feeling about this.