3rd party developers that are used to churning out 3-way (or 4-way) ports of the same title are going to be faced with some decisions. Big publishers might choose to split duties between two different developers, as looks to be the case with the Madden franchise. But don't be surprised if Wii owners start getting gypped because of the console's shortcomings (when compared to the technical power of the PS3 or Xbox 360). The ability to motion to a point on the screen with the Wii controller and fire off a web shot, for example, is certainly no consolation.
Without an obvious advantage, publishers/developers are not going to take risks (i.e. spend millions) to develop truly unique Wii versions of multiplatform titles.