Because you needed more phone punditry from bloviating strangers in your life, I wonder whether anybody truly thinks Apple will stick with the 4" screen in any significant way. Since the release of this year's phones at 4.7" and 5.5", the old form factor seems to me like it's headed for extinction. Plenty of the tech cognoscenti that I follow (so, already, a very specific and narrow set of inputs on which to base my observations) continue to pine for the 4" screen and wonder whether Apple will hang on to that size in future releases.
I think that Apple's move to larger sizes says all we need to know. Hanging on to smaller devices in the $99-to-free price range doesn't look like hedging to me. It just looks like maximizing profits on old hardware.