I doubt they'll ever go that big. Isn't the One something like 4.8"?

It sounds like if Apple ever increases their screen size, it'll be to something more like 4". That way they can stick to the same resolution, and the pixel density should still allow them to use "Retina Display" as a marketing term.

But that's the upshot to the whole "Android fragmentation" issue. You have options, so there's probably a phone with a screen size you'll like. Though to be honest, if you want the best Android phones they'll probably be big screens, since the market seems to be saying that people like them an awful lot...