I doubt it will be soon. COD MW: Reflex ( basically MW1 ) has only recently been released ( NOV 09 ).
I wouldn't expect to see MW2 for a long time on the Wii - if at all.
By all accounts, Reflex has major Framerate issues - I haven't played it, but from reviews it makes it almost unplayable at times.
COD 5 is fun though, worth a go.