You, sir, win my "best new poster of the week" award. Congratulations. 

First, I don't know the actual breakdown of casual vs traditional gamers so far as Wii sales go. I would be willing to venture a guess that a large number of households contain both, so the difference may not be as big as some are making it out to be.

Second, casual gamers often includes adults with well paying jobs and disposable incomes. Its going to be hard to predict exactly what their long term purchases will look like. God knows 8 years ago I would never have predicted that so many casual movie watchers would have purchased so many DVDs.

Thirdly, what Nintendo and Sony and 3rd parties care about is not so much which games are sold as they are how many copies of a given game are sold. So far, Nintendo's top titles are handily outperforming Sony's top titles.  Third parties are especially taking note of this, and are beginning to move their better development teams onto Wii titles. The question is - what are they being moved from?

Finally, you can't really look at WiiPlay or WiiSports as typical games. WS is obviously packed in with the console, so there's no way to tell who would have bought it had it been a separate purchase. And many gamers are buying WiiPlay simply because they want the 2nd controller, and given the success of WS, are willing to spend the extra $10 to give it a shot. Rayman Raving Rabids is a better sample, and that's the 2nd or 3rd best selling Cube game after Zelda. The other game in that trio is, I think, Red Steel, which does appeal to the traditional gamer more than the casual one, so I'm not sure there is any discernable pattern emerging yet. The real test will be when games like Brain Age, EA Playground, and Carnival Games, come out against Mario, Metroid and Smash Bros.

 The real trick here is that Nintendo is trying to engage the casual gamers so that they don't continue the same lacksidasical pattern you cite in previous generations. If Nintendo fails, they may still have enough traditional gamers (who are more interested in the Wii than they ever were in the GCN), but if they are successful (as they have been with the DS), then all past precedent has to be tossed out the window, and Sony and MS will have to hurry up and adjust to a brand new paradigm.

Don't want to break it for you but once upon a time people called DS a fad. I also think that you are underestimating the casual gamers, but that is another matter.

Population grows about 1% every year in the USA. That is a 10% from 10 years ago. Taking absolutely nothing else into account, that means we will sell 10% more consoles even if there are no social changes. An increase of 10% is very significant especially since it represents a change from old to young who are more likely to play games to begin with. Combined with social changes like the increase in gaming popularity in general, this 10 percent can easily account for millions of sales. For reference, there are now about 25mil more people to sell to than 10 years ago just in the US. We arent even talking about china or japan or europe.