According to Kuo, the current design language, which dates back to 2017's iPhone X and has been used in a total of three iPhone generations, will be tossed out the window. In its place will be an all-new design that takes some cues from the revolutionary – at the time – iPhone 4 that debuted in 2010. In a research note that was picked up on by Mac Rumors, Kuo claims that, "The metal frame and the front and rear 2/2.5D glass are still used, but the metal frame surface will be changed to a similar design to the iPhone 4, replacing the current surface design.”
He goes on to indicate that this new metal frame will feature a "more complex segmentation design, new trenching and injection molding procedures, and sapphire or glass cover assembly to protect the trench injection molding structure."
The iPhone 11 and iPhone 11 Pro smartphones feature a more organic chassis design -- aluminum on the former, stainless steel on the latter -- that appears to nearly seamlessly blend into the display glass and the back glass. If Kuo's prediction is accurate, it would seem that Apple will be moving away from the organic shapes that resurfaced with the launch of the iPhone 6 and move towards the more industrial look of the current iPad Pro (which also took some design inspiration from the iPhone 4, albeit on a larger scale).
The change in materials for both the frame and the glass are said to increase Apple’s materials costs for those components anywhere from 20 to 50 percent.
The drastic change in the design language for next year's iPhone was expected, as it will by all counts be the first device from Apple with 5G support. Apple passed on 5G in this year's iPhone release for a number of reasons (delays with Intel's 5G modems, the relative dearth of 5G networks across the globe, etc.), but by 2021 it should be a much more receptive environment for Apple to strike with a 5G iPhone featuring Qualcomm modems.