If the Japanese war had ended before Stalin declared war on Japan, then the Soviets wouldn't have gotten half of Korea. That seems to have been a spur-of-the-moment mistake, to split Korea in two when the Japanese surrendered. Without that, the Korean War wouldn't have happened.
The only winners were the Japanese--the Korean War has been characterized as a Marshall Plan for Japan (since US spending during the war poured so much money into Japan).