Next-generation iPhones likely to focus on internal improvements.
DisplayMate Rates iPhone 5 Screen as "Best Smartphone Display" They've Seen
They conclude that the iPhone 5 represents the best Smartphone screen they've tested.
Based on our extensive Lab measurements the iPhone 5 has a true state-of-the-art accurate display – it’s not perfect and there is plenty of room for improvements (and competitors) but it is the best Smartphone display we have seen to date based on extensive Lab measurements and viewing tests.In particular, they note that the iPhone 5 has much lower screen reflections, a much higher image contrast and screen readability in high ambient lighting and notably improved color accuracy and picture quality.
Here is their Overall Assessments chart comparing the iPhone 4, iPhone 5, and Samsung Galaxy SIII. They conclude the iPhone 5 significantly outperforms the other two units:
The remainder of their charts detail differences in Reflections, Brightness and Contrast, Color and Intensities, Viewing Angles, Power Consumption and Battery Impact.