I don't follow handhelds so no clue :p
Wii hardware does make perfect sense.
Right now they are 4.2 million units or so behind last year at the same time.
October will be like 2008, November will be lower despite NSMBWii.
December will be same or better than 2008 and Q1 2010 will be lower than Q1 2009...
So 20 millions make sense.. Most likely they will end up doing 20.5 millions units or so...