The iPhone 5s was universally loved and it introduced Touch ID. What a great phone. No camera bump, no bending, 64-bit chip, seamless authentication with Touch ID, chamfered edges, beautiful color options -- the thing just felt like a piece of jewelry -- not a gadget.
Contrast that with the iPhone 6 the next year. Clunky rounded edges, camera bump, design that bends, bigger screen without upgraded RAM lead to performance issues due to shared memory between GPU and CPU -- the 6 series sold like crazy because it was a bigger iPhone but it was one of the least loved iPhones. The iPhone 6s series fixed the performance issues and the iPhone 7 series refined it further with camera improvements and some sweet color choices.
But, I don't think we will see a design as nice as the iPhone 5s again given that so much of the feel of that iPhone was due to its small size.
Contrast that with the iPhone 6 the next year. Clunky rounded edges, camera bump, design that bends, bigger screen without upgraded RAM lead to performance issues due to shared memory between GPU and CPU -- the 6 series sold like crazy because it was a bigger iPhone but it was one of the least loved iPhones. The iPhone 6s series fixed the performance issues and the iPhone 7 series refined it further with camera improvements and some sweet color choices.
But, I don't think we will see a design as nice as the iPhone 5s again given that so much of the feel of that iPhone was due to its small size.