Humans are very aggressive and scrappy, and go to war at the drop of a hat. However, a standard land war is no longer going to work as it is no longer technically possible.
They used to be seen as insane or unthinkable acts of madmen. But if they take place they'll be called war too. And there will still be no conventional war.
War as Napoleon knew it just not possible any more. However, we're very unlikely to accept or recognize world peace even when we get it.
We may yet work up to some serious shooting war, or maybe some acts of urban genocide committed with rogue nuclear weapons. But if that were the case, why would we call that 9/11? If Washington disappeared in a mushroom cloud, we'd give that huge event a different name.