With how expensive videogame development is becomming and how different the Wii is from the PS3/XBox 360 shifting the focus of large publishers is a lot like turning an oil tanker; it can be done but it takes a long time.
Before the XBox 360 was released companies like EA began switching their development resorces away from "previous generation" consoles towards "current generation" HD consoles; being how similar in performance these systems were going to be these publishers believed they could share the majority of their resources across platforms to manage expolding development costs. I don't think in 2004 these companies anticipated a low performance console being as popular as the Wii has become.
Until the Wii was released many publishers only had token support planned for the Wii because it was their belief that improved graphics were what really sold consoles.
Now, EA has spent so much money developing games for the PS3 and XBox 360 that they simply can not cancel "Fifa 2008" (as an example) in order to divert resources towards the Wii to produce NHL 2008 for the Wii; this means they have to either create a new developer, buy a developer or wait until a developer becomes "free" before they can move forward with NHL 2008 for the Wii. I know for a fact that EA has been buying developers and creating new internal development teams to handle Wii projects and it is (remarkably) likely that development resources will be shifted towards the Wii as projects are completed; this shift may be as simple as reducing the number of developers working on Madden/NHL/Fifa 2009 because they already have a working game and can produce their next version as a "Roster Update", or as complicated as converting a development team to produce Wii projects after they finish their XBox 360/PS3/PSP/PS2 game.
