OK- I understand why the new resolution would be frustrating, but- if they keep the same aspect ratio, would it really be a "nightmare?" I mean, when they doubled to the retina display they simply scaled everything by 2x and gradually app developers added in the bitmap graphics as updates to their apps.
If apple went to a 4" screen, I would imagine they would go from a resolution of 960 by 640 to 1280 by 800, or maybe 1280 y 720, IF they increased the resolution. So the apps could just scale the native iOS graphics and stretch the bitmap graphics until developers upgrade their apps with, say, a "3x" extension...
I don't know- I just think that as long as the aspect ratio is maintained, unless I am missing something, it would not be a huge nightmare for developers.