I expect there are a few people who are shorting the South Korean won, who would definitely want war to break out. If North Korea makes an outright hostile move against another nation, it will likely be met by disabling strikes from the military of all the nearby nations. Kim Jong Un, in a last-ditch effort to retain power in North Korea even if nowhere else, would respond by doing his best to flatten Seoul. He'd probably manage to destroy a decent portion of the city, which would have disastrous effects on the won - it's already wavered a bit lately with all the tension.

That being said, I also think it's unlikely. Kim Jong Un is no madman, and he'd have to be to actually launch an attack first. Trump is also no madman, despite appearances, and he knows he's close to being impeached already. If he loses the support of the rest of the country by starting WW3 with a pre-emptive strike on North Korea, even after every world government has announced that they will not support the US in that situation, he'd be gone as near instantly as things can ever happen with big government; probably a week or two at most. He's already got a pretty substantial case built against him for obstruction of justice, which will only be averted by the fact that Republicans control the entire government and can ignore anything they find inconvenient - and don't get me wrong, Democrats can, and do, ignore everything they find inconvenient most of the time as well. I'm a moderate myself, and simply expressing frustration with the fact that our government is a loud, partisan nightmare that can't legislate its way out of a paper bag.