North Korea has now officially declared war with the South
No, they haven’t. They have said that they are in “state of war” with the South, and that every decision they make will be made with this in mind. They’re not actually at war, because a) they’ve technically been at war with the South for the past sixty years, and b) they haven’t actually done anything that could be considered an act of war.
I honestly doubt that the Korean Grand Prix will be cancelled, except in the case of a nuclear shortage. For one, the North seems to have abandoned its idea of uniting the Koreas by force, and is instead concentrating on attacking – verbally for the moment, but they claim a military strike is not far away – the United States. They see the United States as being the perpetrator of every grave injustice, and are more interested in threatening them than they are their neighbours; perhaps they feel that if they can wound America’s pride enough, the South will capitulate and join with the North, having awakened to America’s imperialist oppression.
However, an actual war would be unlikely to threaten the race because it would be over very quickly. Despite having the fourth-greatest army on the face of the earth, the North’s soliders use weapons and equipment that the Soviet Union deemed unuseable, and the bulk of their firepower is aimed directly at Seoul. It would take a matter of hours for America and the South to target and destroy their artillery positions, and despite having nuclear weapons, the North does not actually have the ability to deliver them via missile – which means they need a bomber, which would be easily intercepted. Any war would likely reduce North Korea to a smouldering crater in the space of a few days. The West using nuclear weapons is out of the question, because they’re unnecessary and because the fallout would have the potential to affect over three billion people.
Given the distance from Seoul and its relative strategic unimportance, it would not be likely for Mokpo – the site of the circuit – to be affected by such a war. Provided that Seoul stands, the race will probably go ahead.