As the Wii becomes more dominant, is it inevitable that publishers will spend more money on major titles for the Wii, which is the first step toward improving quality.
In order to justify more money spent, one of the big things the Wii needs to do is to obtain enough marketshare to make the PS2 (not PS3 -- the PS2) no longer viable for cross-platform development. I would go as far to say that, at this point, the PS2's continued existance, in huge numbers, is the only thing holding 3rd parties back from making decent games on the Wii at all. Instead of dumbing down games for the PS2, they could be making Wii exclusives... but aren't.
I would say that the Wii needs to obtain something close to 55% marketshare (very doable), and a raw 60M units in existance (to make the PS2 significantly less effective for cross platform appeal -- probably not until late next year). I think that the 3rd party publishers are already beginning to realize that the Wii is likely to meet these criteria sometime late next year, and are starting to look at spending more money on Wii exclusives -- and thus, better quality titles... in a year or so.