After seeing Japan beating Greece, I guess we can say that Japan is actually ready to fight for the championship. Although Japan was ranked twenty something in the previous ranking, the ranking probably did not include players like Tokugawa, Oni, Irie, Tanegashima and all the overpowered MSers.
Tanegashima beat Zeus suggested that Byodouin, Oni and Tokugawa would probably be able to beat Zeus. So there are at least four players that are able to beat the strongest player of the world number 10 team. Ochi played evenly against one of the best Greek player (considering Hercules saved a move against Germany, he should be a top 5 Greek player)
I would say Japan's current ranking is somewhere between no. 6 and 9. (actually I would say they are merely weaker than the big 4 and the US) Obviously, they will get power up during their match against these strong countries and their ranking will go higher later on. Australia and Switzerland would probably send their strongest team against Japan. I guess Australia would only be able to threaten Japan just because they send out their best players meanwhile Japan is sending their relatively weak player (i.e. Date, Gin and Nakagauchi) and we will have Atobe beating the best Australian HSer.