This is similar to Apple's strategy with the iPod. Start out with a premium device, then create new devices to fill lower price points.
I am curious with the iPhone as to how they would differentiate the lower priced device from the higher price.
I'd guess a different form factor and a screen the size of the 4S - Plastic or some sort of non-conductive metal shell in a few different colors. Maybe leave out LTE for the first generation. iPhone nano? iPhone mini? And I wonder how thin they can make it...
They already do this. They use lower end processors, screens and strip out new features of the current iOS. They may all be on the same version of iOS but they are not the same. Lack of Maps, Siri are examples of Apple fragmentation. The only difference is Android updates their OS level when they add new features.