Rumors from sources supposedly familiar with the matter suggest that Apple is trying to manufacture the upcoming iPhone 6 with a thickness that will not exceed 6mm.
According to the Chinese website ET News:
“Apple’s upcoming iPhone is known to be already in development and is expected to be released this year. It will be very thin, while the weight of the metal frame is reportedly expected to increase slightly.”
The website says the device will be 6mm thick, which is quite thin even by Apple's standards. According to the same sources, Apple wants to achieve half the thickness of the iPhone 3GS, which was 12mm thick.
The frame will continue to be made of metal, and there will be two models. One with a 4.7-inch screen and the other with a screen that will be almost six inches – essentially we will see the first phablet from Apple.

