If Activision still has plans for releasing a special edition headset for Call of Duty on all consoles, then it looks like the Wii is going to get Modern Warfare 3 even though it never got MW2 in the series (MW 1 was renamed MW Reflex on the Wii).
Officially, Activision and IW haven't confirmed nor denied the Wii version is in development. Originally, the previous bosses at IW never wanted any of their games on the Wii which is why Activision used Treyarch for the Wii games in the series. Now with those guys gone and Battlefield 3 being a serious contender, a Wii version would add another source of sales for this year's CoD game (Wii versions usually get about 1.5 million in sales).
http://www.nintendoworldreport.com/news/26684