Curiously, the game will be missing "some" of the missions present in the Xbox 360 version (and less curiously, an online component). The Wii launch will likely fall after Double Agent's October debut, so the cause doesn't appear to be an unreasonable restriction in development time. A few missions for a different control scheme -- is that a fair trade? While it's certainly possible that Ubisoft will include extra missions more closely designed with the Wii controller in mind, that seems unlikely given the platform differences in past Splinter Cell titles. After all, there are seven other motion-sensitive games that need to be bitten off and chewed before the Wii's launch later this year.
[Thanks AssemblyLineHuman and Jeremy.]