Remember how gigantic the iPhone's 3.5-inch touch display seemed when the handset arrived in 2007? Fast-forward five years and a lot has changed. The success of 4- to 5-inch Android phones, particularly Samsung's and HTC's fleet of big-screen models, has made the iPhone's display look puny by comparison. How big will the next-gen iPhone's display be? Rumors abound from numerous sources, most of which predict a screen measuring around 4 inches diagonally--a subtle increase over the iPhone 4S.