As long as videogame companies can make enough money to justify making these graphically impressive games they will continue to be made. The Wii being the most popular system in the generation (even by a long shot) will not impact the ability for developers to be profitable with these games. Basically, if you can't produce a game that is profitable after being released for the XBox 360, PS3 and PC then the game was not going to be profitable if it was released on a system with a 100 million person userbase.
Will we see less of these games?
Probably, but I would say that is a good thing. In the last 2 generations producing pretty trash has been an adequate strategy for making money; a 4 hour game that has pretty graphics but shallow, boring gameplay was easily able to break even by releasing screenshots to hype the fanboys. Companies will have to focus more on making interesting grapically impressive games to ensure they get the sales they need, or to produce interesting less graphically impressive games because screenshots alone will not be able to easily hype people.