No, not a fucking chance. iPhone as a phone/mp3 player is great, but as a gaming machine it sucks shit out of a cow's ass. I have an iTouch and I love it for music but the games suck. My most played game is fucking paper toss.
The graphics suck, the controls suck (physical buttons >>>>>>>>>>> touch screen) and the screen is small.
Traditional handheld gaming isn't dying anytime soon.