Mate, Japan isn't even that better than West Asian teams like Saudi Arabia and Iran, let alone African teams. Japan while possibly being the best Asian team in the last decade, i feel gets a bit overrated sometimes, i don't regularly watch or follow Japanese football, but i do watch them play in the Asian Cup and i do watch them play in qualifiers whenever they play an Arab team. Did you watch them in the last Asian Cup? They were an ordinary team.
Japan have won 3 out of the last 5 Asian Cups? They also didn't do bad at all in 2007, won the group easily, beat Australia on pens and then narrowly lost to the Saudis in the semi. Besides, development is not all about results. I've seen Japan draw at Wembley, when most smaller sides get turned over 3-0 to 5-0 in those friendly matches, but on a bad day they might have indeed lost 5-0. Japanese, like most east Asian teams, don't travel so well to the Gulf, and vice-versa. I've watched many Arab teams come to Yokohama and take a pretty good stuffing, sometimes saved by that problematic finishing problem. It's a very long way from Tokyo to the Middle East, this is a big problem faced by Asian teams.
I also never said Japan were better than African teams, I used the comparison that African teams benefit directly from European football whereas east Asian teams have to go it alone. In Japan they did with football what they have done with everything since the country made contact with the West. They look at what is the best in every area and copy it. With football they took on the Brazilian style, and they can all play lovely football but suffer on the physical side, although that has changed a lot in the 12 or 13 years I have been watching. Arabic teams don't have this problem because ethnically they are more mixed and various in terms of physique, in east Asian there is little variation.
I do think that either way it will be a long time before we see a very strong Asian team, and it will more likely be from a middle eastern side because more will make the jump to the strong European leagues as the cultural differences are big, but not as great. Japanese players often turn down moves to European sides, money is good and it is too much of a change. Marcus Tanaka was one who had offers from England, France and other places when his contract was up in December, but he just swapped J.League teams instead, and at 28 it was his last chance to move.
As for the World Cup I don't fancy the chances of Japan much, as I do not like Okada the coach, he and his results are just not as good as Osim or Zico. In a group with Cameroon, Netherlands and Denmark that is extremely tough and there are problems in attack.