I cant see the Iphone being something that parent buy for their kids to play games on... that is the heart and sole of the DS market, yea they got some older people with the Brain Age games and such, but Kids are never gonna leave Ninty.
I could see the Brain Age Crowd migrating in small numbers to the iphone gaming however.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut