Even if third parties give up on Wii in Japan aside from a few major titles like DQ10, you still shouldn't underestimate the impact of a price cut to maintain what remains of the market. Nintendo doesn't include any games with Wii in Japan, so the Wii at 20,000 Yen is really selling for $50-$100 more than it is in USA, depending on how you value Wii Sports / Wii Sports Resort.
Wii doesn't look like it will ever sell 3m in Japan again, but with what should be coming (Mario Sports Mix, leggy sw in late 2010, Pikmin 3, Dragon Quest X, Zelda, Inazuma Eleven, and the Vitality Sensor game, probably a price cut), there isn't really any reason why Wii can't stabilize at 1.5m - 2m for a year or two before returning to steady declines.
At some point I do think we'll see one or two more big third party projects for Wii in Japan. With DS / PSP set to decline as 3DS arrives, there should be a point in 2011 or 2012, where given DQX and a 12.5m base, Wii might be the biggest RPG / Core base as it will take time for PSP2 / 3DS to ramp up. Kingdom Hearts would probably do fairly well on Wii in this time frame, just ahead or after DQX.
I do think PSP2 is going to be unveiled at CES 2011 or GDC 2011 or Dice 2011 - sometime in Q1 2011, and will probably arrive by early 2012 worldwide...but DS / PSP are going to be pretty dead in Japan after 2011 and 3DS will be just entering its best years so Wii probably becomes the optimal base, by size for a time for a little while in Japan in 2011 or 2012.
People are difficult to govern because they have too much knowledge.
When there are more laws, there are more criminals.
- Lao Tzu
