Apple's rumored next step is releasing a budget or cheaper iPhone, as to appeal to emerging markets. The budget iPhone is rumored to be released alongside the iPhone 5S and iOS 7 later this fall. Current rumors that the device will feature an A5 processor, cheaper components, as well as a polycarbonate plastic back.
Recent leaks have shown the rumored plastic back in several colors. The latest photos come from developer Sonny Dickson, showing the plastic rear shell next to an iPhone 5 rear shell. As seen in the images, the budget iPhone will have a cheap pastic feel to it, similar to Samsung's Galaxy S phones.
Source: https://twitter.com/sonnydickson