I'm personally starting to think that the Wii audience has been let down too much (3rd party wise) to bother investing in the system anymore.
You've got a percentage of the casual audience eventually realizing that what they're buying is crap (tired minigame shovelware whatever)
Then you've got the core audience just always eagerly awaiting something only to realize it's a spin-off, port, niche, on-rails or whatever.
It comes to a point when after years of rubbish (or perceived rubbish), ppl are get so burnt that even if 3rd parties start producing commercial high quality products, it might be too late.
Just a thought.