ME I don't fully agree..IMO realistically speaking:
North Korea has no chance at all and just has to make the losses as small as possible.
Australia has the toughest group. Germany is the favourite, Serbia's a strong team and Ghana's unpredictable. They'll be fighting for 2nd place, although I think Serbia's stronger. They have to hope for Serbia's lack of scoring ability to show. They can beat an inexperienced Ghana side, but it's a difficult group and it'll be tough for Australia to go through and I don't think they will.
Japan's group is simple: Holland will win it, the other 3 will fight for 2nd spot. And all 3 are more or less of the same level IMO. So Japan has a good chance if things go their way, and they can just as well be 4th if things don't (just like Denmark and Cameroon).
South Korea has the easiest group of the Asian teams. Argentina is by far the favourite, but South Korea has a good chance of finishing 2nd. Nigeria is not impressive and also doesn't have their best player, and Greece is also beatable for them.
In short: North Korea is chanceless, Australia's group is too hard, Japan has a 1 in 3 chance and South Korea's has the best chance of going through.