The fact is --
- The system is 3 years old and still doesn't have a big-budget RPG out for it.
- Monster Hunter 3 was the first big third party game for the system and that took almost 3 years to come to market.
- Nintendo themselves have had a mediocre release schedule for the prior year with Animal Crossing + Wii Music last fall and nothing notable for the first six months of this year. Basically since they release Mario Kart Wii a year and a half ago they haven't had a blockbuster title for the system.
- Wii Sports Resort and Wii Fit Plus while big name sequels do not bring the "freshness" and "newness" to the table that their originals brought, which was probably a big part of the appeal. So the sequels are selling great, but they are not driving hardware sales as much.
I think all that essentially has caught up to the Wii. They will probably have to regroup next year and see if Wii Vitality Sensor -- which is a completely new kind of idea can re-ignite sales I think (Japan is a stressed out society ... well so is the US, but Japan especially, so that could take off if done right). Nintendo needs to take the third party thing more seriously.
It's unacceptable to have a platform go THREE YEARS without any major third party support and think nothing bad could happen. That cannot ever happen again ... sometimes unfortunately, Nintendo has to learn things the hard way before they change.
I think Wii 2 could be coming sooner to Japan than the US/Europe too if the Wii does not shake off these doldrums. Obviously sales will pick up for the holidays (even the GameCube sold well during the holidays in Japan), but if its back to struggling come January, I think Nintendo may have to acknowledge they may need a mulligan on the Japanese market.