At the mall, I noticed that more people use 2 hands than 1 hand. Seems like the youngest use 1 handed the most, probably casual social media use. Bottom line is this:the growing majority don't just see it as a phone, they see it as a mobile computing device. and if given the choice, most would prefer to carry around one mobile device, not two (or three)... and it is there that a larger iPhone would be valuable. I can see a 4.7" iPhone on the very near horizon. 5.5" later.