I wonder if Apple is confounded by its own naming scheme (iPhone 5, 6, 7 . . .).
With the Mac they have established product lines they iterate on.
Yet to make a lower-specced iPhone 5s, they came out with a iPhone 5c.
And now to make a higher-specced iPhone 5s, they're coming out with an iPhone 6c.
The iPhone 5/s has the perfect design. It seems like they're trying to contort their ideas on what they want to sell into a new product name and then believe that new product must have a new design.
The MacBook Pro has looked essentially the same since 2008, when the unibody design came out. And they've regularly upgraded the specs without having an all new design or complicated numbering and lettering scheme.
I think the iPhone 5s is the absolute perfect design. I would love to see it improved with an even better display of the same size, OIS camera, faster processor, Apple Pay, and more RAM. I think it would be the perfect phone.