What all of the leaked photos tell us about Apple’s latest device.

A couple weeks ago, as part of documents disclosed in Apple’s patent case against Samsung, we discovered that Apple’s 2006 prototypes of the iPhone look pretty similar to the iPhone 4, which was released in 2010. In other words, even before the first iPhone was ever released, Apple had an idea of what it wanted the iPhone to eventually look like. The first iPhone—which was launched in the summer of 2007—didn’t quite get there. Neither did the second, nor the third. But by the fourth version, Apple had found the natural design for the iPhone, and unless some radical new technology comes along (flexible screens or some such), we can expect every new iPhone to be cut from the same cloth.

This is going to bother some people. “If the iPhone 5 looks like the pictures that have recently appeared, Apple may be screwed,” Business Insider’s Henry Blodget wrote in July. Blodget, echoing others, complained that the phone just didn’t look new enough—while Apple’s rivals spent the last couple years creating phones that look like “next-generation” devices, Apple’s design seems stuck in a rut.

The trouble with such arguments is that they rarely identify how Apple could improve on the iPhone’s design. Blodget’s main problem with the current iPhone is that it is “small”; Apple’s rivals have steadily been increasing the size of their phones, while Apple has refused to do so. Even if the new model is slightly taller, its overall dimensions will be far smaller than most other devices in its class.

But I think Apple has calculated, reasonably, that most people don’t want enormous phones. As I wrote in February: “A larger phone is more trouble to carry around than a small one, it’s harder to hold and use with one hand, it usually gets worse battery life, and when you put it up to your ear, you’re liable to get swept up by a strong gust.” There could well be some people who genuinely prefer larger phones, but they’ve already moved on to other devices. For the tens of millions of happy iPhone customers around the world, including me, the iPhone’s size is pretty on target.

And other than changing the size, what else could Apple have improved about the iPhone’s design? Not much. Way back in 2010, I predicted that the iPhone—and smartphones generally—had reached the limits of industrial design. As long as we’re going to interact with our phones via touchscreens, the iPhone will continue to look like a slab of glass bordered by some metal. Apple will tinker with things on the back, top, and sides of the device, but these will all be minor details.

Other than that, expect the overall look of the iPhone to be more or less set in stone for at least the next three or four years. Apple simply doesn’t make big design changes just for the sake of making something look different—it’s always looking for something better, and if it has already created something great, changing it for the sake of change won’t do anyone any good.