If Apple considers a screen size of 4.5- or 4.8- instead of
5-inches, the basic premises stay the same. Either way, if Apple
stays at 2x, interface elements wouldn’t be blown up as much at
4.5- or 4.8- as they would at 5-inches, nor would density decrease
as much. At 4.5-inches the current 1136 × 640 display would be
290ppi, and at 4.8-inches it would be 272ppi. 3x would be 435ppi
or 408ppi. 4x would be a silly 560ppi or 543ppi.
3x or 4x isn’t happening any time soon. The most likely scenario for a bigger-display iPhone would be to keep the same pixel count as the iPhone 5 (1136 × 640)
and use the 264 ppi density of the retina iPad. My arithmetic is a little different than Ritchie; I got 4.9 inches diagonal for a 264 ppi 1136 × 640 display.
Think about what Apple did when they made the iPad Mini. They kept the pixel dimensions the same as the non-retina 9.7-inch iPads, and used a display with the exact same pixel density (163 ppi) as previous devices (the original iPhone, iPhone 3G, and 3GS). From an operations standpoint, they’d be re-using a component they’re already familiar with. From a software standpoint, existing apps would just run, and everything would just look bigger on screen.
I haven’t heard even a whisper about such a device actually being in the works (but Jeremy Horwitz has), but if it is, that’s how I think Apple would do it.
★ Monday, 28 January 2013