His picks for cabinet show that he's completely dangerous.
He might not start ww3, but he might cause a lot of riots and maybe even a revolution, depending on how badly he treats "minorities".
Actually, I think his picks for cabinet show that he is, and will be, controlled by the Republican Party after all. He's shown that his anti-establishmentarianism was just unsupportable rhetoric.
In which case, I don't think the WW3 risk is as high as it could have been, because an annihilated world would play hell with the stock market.