Since 2007, Apple has changed the size of the screen on the iPhone. The first two iPhones had a 3.5-inch screen with a 320×480 pixel resolution.
The iPhone 4 changed the resolution boasting a new ‘Retina Display’ at a 960×640 resolution;
The iPhone 5 changed the screen once again to better suit widescreen content. The screen was now 0.5″ bigger at 4″ with a resolution boost up to 1136×640.
The iPhone saw the biggest change to screen size with the introduction of two entirely new screen size models. The iPhone with 4.7″ screen size and resolution of 1334×750 and the iPhone Plus with as 5.5″ screen size and a resolution of 1920×1080.
So with Apple being so happy to change the screensize and resolution of their iPhone, it is quite possible that they will opt for edge to edge display completely removing the bezels and making a much sharper looking phone. Like portrayed in this mockup;
Or could they follow in the footsteps of the Samsungs Galaxy S6 Edge which sees the screen wrap around the edges to give more immersive experience;
References;
https://en.wikipedia.org/wiki/IPhone_(1st_generation)
https://en.wikipedia.org/wiki/IPhone_6