What puzzles me is why third parties care about the future of a platform that they never make their best games for.
Third parties seem to regard the Wii as something different and thus they give it different games than what the other consoles get. But they might not like it to be that way. In Square Enix's case they've invested a lot of time and money in Final Fantasy XIII and they're going to release it on the PS3 and Xbox 360. But that effectively limits FF13's potential sales. Ideally they would want to release it on all three platforms for maximum potential sales. But they can't release it on the Wii without investing even more money into downgrading the visuals to work on Wii hardware. And even if they did that they might fear that the downgraded visuals and the stigma of being a scaled down port may hurt the game's marketability with its target market.
The Wii quite clearly has a technical hurdle in that it's severly underpowered compared to the other two consoles. When Capcom released Dead Rising on the Wii I think they legitimately wanted to just port the game over but found out that they couldn't.
If the Wii was an Xbox 360 with the remote as the controller I really doubt it be missing out on all these games that both of the other consoles get. Why wouldn't they release these games on all three consoles if they could and thus make their game available to the widest potential customer base? Now they probably could or just should make the Wii their target platform but they're not and that's a different topic.
If the Wii 2 was comparable to the other consoles in hardware then third parties could release anything they wanted to on it. All their casual focused shovelware could still be on there, too. It provides them with no restrictions. They want all three consoles to be as similar as possible so that they can make whatever game they want on whatever console they want.
As for Nintendo, well this is all about third party support and that directly affects customer satisfaction and product image. It should be in Nintendo's own interests that videogame customers of all tastes be satisfied with their console's library and for their console to be associated with quality games (ie: associating the Wii, and thus Nintendo, with shovelware trash is not good). But they very much live in the present and since this is not causing them any obvious problems now I don't expect them to feel it's any priority until it becomes so. So they probably SHOULD release a new Wii by 2011 but they probably won't until they're forced to. In other words it's only after they start losing market share to the competition that they'll get off their butts. But they almost certainly have some sort of next-gen console in the design phases so it's not likely they would be completely caught with their dick in their hands.