And as processors get more powerful, more functions will appear, and likely will match or surpass real cameras in quality. A great example is the HDR function in the iPhone 4 and higher. If that is just step one, we should see more and more functions that will make taking professional pictures easier to pick up.
However, I'm not against the normal high-end cameras. If they do work better, it's fine with me. But with the rising speed of computer processors, are they going to be replaced? Anything can happen in the world of technology nowadays.
The parentheses were put there as like a "think about it". There is not much of a possibility that Iphone/Android apps could ever take over console gaming (aka the "pro" gamers*) but they can take over mobile gaming, (the "casual" players*). In a same sense the camera can replace digital or "casual" camera, but wouldn't really be up to par with the more expensive "pro" cameras.
*I know that not all console gamers are hardcore and and all mobile gamers are not. What I'm saying is that it will appeal more to the smaller, handheld on the go type people.