I can't imagine that they just failed to observer the demand for smaller form factors. For one they surely have pretty accurate data on what most customers real

I can't imagine that they just failed to observer the demand for smaller form factors. For one they surely have pretty accurate data on what most customers really want and they are still selling the 5S. If they see that demand for the 5S is higher than expected or that too many customers are unhappy with the larger devices they will accept this reality and release an updated iPhone 6S that is smaller.