Bigger iPhone Screen without Fragmentation: Here's How
Yes, Apple can make the iPhone screen bigger without fragmentation There are two criteria they'd need to meet:
1- Maintain a DPI of over 300 to preserve Retina brand
2- Provide backward compatibility with pre-existing apps
Here's how they can do it:
Step 1: Double the current resolution
Step 2: Spread out the pixels
This lets Apple keep compatibility with all previous apps, and give some developers the edge of developing for the larger screen. Much like the transition we experienced when the iPhone 4 came out.
Tim Cook said that they have to wait for the right time. The time will be right once 400+ DPI screens become viable for production at Apple's scale.