Controversial opinion here, but I think nukes are going to be an evolutionary dead-end in the history of weaponry. Either they'll end up getting used, in which case "WW4 will be fought with sticks and stones", or more likely they won't end up getting used because everybody knows that's the outcome, and we'll have more conventional proxy wars where everyone just pretends nukes don't exist.

Other controversial opinion: I think that the assumption that the next major war will be between nation-states is a likely candidate for one that'll go out the window. In my view, the next major war will be like Syria but on a global scale, with many semi-organized subnational groups duking it out in exceptionally nasty urban & guerilla warfare.

I thought those were both mainstream opinions.