Notice, I didn't say everyone. If you read my post before going into 4" defense mode. Yes, of course there are people who genuinely prefer smaller phones and I respect that. However, I stand by my post. I still a significant portion of the people complaining about the size of the 6/6S are only complaining because it's a change without actually trying out the phone.
I still maintain thats not true. I did read your post.
Until Apple actually offers an iPhone in all three sizes in one series, we won't truly know where people's preferences are. I'd suggest in that case that the 4.7 would be the biggest seller and the 4 and 5.5 would both have similar sales numbers.
But at the end of the day, there are even plenty of people who bought a 4.7 inch iPhone and would prefer a 4 inch phone, and as I said before, Apple should be focused on the best experience for customers, rather than just looking at sales numbers. A person who prefers a 4 inch iPhone, but buys a 4.7 inch iPhone as they're locked into the ecosystem or other reasons, then that person is not going to be as satisfied as if Apple offered them a more suitable size.
I can almost guarantee that a 4 inch iPhone would sell. Apple was willing to spend money developing an update for the iPod Touch, even though it sells in such few numbers, and a 4 inch iPhone would sell more than that.