There's a difference between 'SquareEnix' and 'Yuji Horii'. Yuji Horii always makes his games for the system that is 'in the lead'. And that is the DS and Wii. Plus, eventhough a number of third party games have done poorly on the Wii, that has been due to bad marketing and support from their parent company. When a company actually puts forth the effort, they get positive results, such as the RE titles, Monster Hunter Tri, WiiSki, etc.
Dragon Quest X will be a success no matter how you look at it. Wherever they put it, the Japanese gamers will go. It probably won't sell as well as DQIX, but it'll still see those high million sales like its predecessors. And I'd be willing to bet it sells at least as well as DQVIII. Especially since it'll be coming out at near or the very end of the systems life cycle.
The trick is getting the international market interested in Dragon Quest. Something SquareEnix has been dropping the ball on over and over and over again with lackluster localizations and NO marketing. Nintendo is even having to come in and market the next title for them to help make Dragon Quest popular, even after they have had 8 years and 6 titles to do so on their own, talk about sad.











