Some have speculated that Apple would maintain the current 326 ppi density, and bump the resolution to 1334 x 750. However, according to the report, Apple plans to triple the 'base' number of pixels on the iPhone screen from 568 x 320 and expand it to 1704 x 960. This would keep the current 16:9 ratio of the iPhone and keep the Retina branding.
Apple is preparing to make another significant screen adjustment to the iPhone. Instead of retaining the current resolution, sources familiar with the testing of at least one next-generation iPhone model say that Apple plans to scale the next iPhone display with a pixel-tripling (3X) mode.
This means that Apple will likely be tripling the aforementioned “base resolution” (568 x 320) of the iPhone screen in both directions, and that the iPhone screen resolution will be scaled with an increase of 150% from the current 2X resolution of 1136 x 640. Of course, Apple tests several different iPhones and display technologies, so it is possible that Apple chooses to take another route for display specifications for the 2014 iPhone upgrade.
568 tripled is 1704 and 320 tripled is 960, and sources indicate that Apple is testing a 1704 x 960 resolution display for the iPhone 6. Tripling the iPhone 5′s base resolution would mean that the iPhone 6′s screen will retain the same 16:9 aspect ratio as the iPhone 5, iPhone 5s, and iPhone 5c.
The larger screen would mean iOS's user-interface will become larger and sharper unless Apple decides to optimize iOS for the larger screens. Sources claim that core user interface elements will simply appear larger than what we currently see on iPhones today.
Apple has been testing this resolution, however it is not clear if it has decided to go with it for the final product. The iPhone 6 still is a few months away, but you can expect a faster A8 processor and an upgraded camera to come along with the new phone.