Re: @Mark - multiple iDevice resolutions
Well I'm not saying it's an difficult problem, just that the advantages of "single model" aren't there, and it's no worse than other platforms like Android.
"So it's unlikely app developers will ever need to worry about more screen dimensions they do currently, as any newer screen dimensions (from say a phablet type iPhone) would come around the time you'd eliminate one of the older ones."
Even currently, there are still 4 sizes (the 4/4S is still in widespread use), and I think at least 3 resolutions?
Plus look at it from the other way - suppose I wrote an application a few years ago, isn't it better that all the existing applications Just Work, rather than breaking (or needing some horrendous hack, or leaving blank space)? If a new model is released, I want it to work out of the box, not have to rewrite all my apps. This is bad for both developers and users.
"Apple could do a more major update to iOS at some point and have it use Quartz for full resolution independence like OS X does. That they didn't do this when iOS first came out could have been due to battery life concerns from the computational load, but now CPUs in phones are far more powerful and efficient so it may be a reasonable thing to do."
Wait - are you telling me that the IOS API *doesn't* have a UI toolkit with resolution independence? What, are apps specifying coordinates like it's 1990 again?
The low CPU power argument doesn't really hold - the iphones have always been high end devices, and Symbian has had Qt (with still excellent battery life) that runs on even mid-range phones from 2008 (e.g., Nokia 5800 with 433MHz ARM11, no GPU).