I saw more of a chance of that with McCain. Following his career ever since he arrived here in Arizona, I could imagine we'd be up at least up to WW#5 by now. The guy consistently wants the country to stick its nose everyplace and the only solution he ever see is the military. I could understand it, that's his background.
Now getting back to Obama, I think the chance of world war would be purely ineptitude of putting the country into a position it couldn't back out of, but I think he's done enough to keep other nations respectful of our military. I see Trump as similar in this regard.