Maybe, but I have a mix, my partner has a large phone and carries a backpack(!?) with her everywhere, but her closest friend has an iPhone 5 (which she doesn't update the OS on because "it will get slower").

So in my circles it's already 50/50. But I do see iPhone 5's and SE's amongst my circles more commonly than I should given the age of the phone. I'm not 100% on why, though I often ask. And it's incredibly rare that it's a cost decision.