I take that as they want to make sure the audience is still there before committing to MW2. If MW1 sells at least as well as WaW, I think MW2 is a shoe-in for Wii.
Basically, they probably view the Wii audience as uncertain, so they want to make sure that each step is secure before committing to the next one. Also, Modern Warfare is going to basically be its own series, after all, so from that perspective, the sales of CoD3 and WaW aren't as telling.
What I'm
most pumped about is that they're wholesale copying The Conduit's controls.
Every FPS on Wii needs to do this.