Several rumors about the higher resolution and how these changes could affect developers have circulated recently.
Retina technology currently used in Apple’s 2x mode means doubling the number of pixels compared to the basic resolution.
With the iPhone 6, Apple would change the current “2x” pixel doubling technique for Retina quality to a “3x” technique.
This would triple the basic resolution of the iPhone, which is 568 x 320, but keep the same 16:09 aspect ratio that is found on the iPhone 5/5S/5C.
As demonstrated by this user, optimizing applications from 2x to 3x results in a much sharper interface.
See below the changes from the previous increase from 1x to 2x, and how the image quality might be better on the iPhone 6.