The iPhone's reign of supremacy is ending, but its successor won't be a single device, says Owen Hopkins.

The age of Apple is coming to an end, that is if you believe the reaction to the company's dramatic announcement that it was going to miss its revenue targets this quarter, now confirmed in the financial results reported this week.

After being one quarter away from bankruptcy in 1997, Apple last year became the first company in world history to be valued at $1 trillion (although it's now worth a little over $700 billion). Driving that extraordinary growth for the last decade has been the iPhone, the single most successful consumer product in history, and one that has quite fundamentally changed how we live. But as sales begin to tail off, many are now questioning whether its lustre is beginning to tarnish.

The iPhone has reached the end of the road

The name of the product was always something of a misnomer. Steve Jobs' insight was that the iPhone was actually a powerful network-enabled computer with a built-in screen, which you could carry in your pocket. His and Apple's genius was to create an intuitive interface which made that computer usable by the masses. And when they created the App Store with iPhone OS 2.0 in 2008, the world piled in.

Apps have changed how we travel (Uber), how we date (Tinder), how we communicate (iMessage, WhatsApp), how we argue (Twitter), how we share photos (Instagram), how we navigate (Google Maps), and so on. It's hard to imagine a world before them.

But after 12 years of stunning growth, the iPhone has reached the end of the road – or so many are predicting. In reality, Apple's sales have been mostly flat for a few years now, as growth in the smartphone industry as a whole has slowed down. Even Samsung, Apple's arch rival, has recently announced that its profits for the latest quarter are well down.

This is the reality of a mature market. Growth in the first decade was driven by people buying their first smartphone, expansion into new geographical markets, and rapid technological advancement driving frequent upgrades. All of these areas of growth are drying up. None of this has caught Apple by surprise; there are signs they are already adapting their strategy.

Its very success has created resistance to change

Some observers have attributed the slowdown in sales to the fact that the price of iPhone has increased over the last few years, with the iPhone X the first to break the $1,000 barrier. But it's not that Apple has been greedily increasing its prices, it's actually that it decided to make more expensive iPhones. As the upgrade cycle gets longer, with typical consumers buying a new phone every three to four years rather than every one or two, Apple has calculated that people might spend a little more on a higher-end product.

In time, we're likely to see a transition from one-off payments to "iPhone as a service" in which most consumers pay a subscription and get a new phone regularly.

While smartphones are getting faster and faster, and their cameras better and better, they aren't fundamentally changing. The Apple blogger John Gruber recently drew attention to how much the original Mac OS had progressed over its first decade and how comparatively little iOS has changed over the equivalent time, suggesting that the latter needs to evolve. But what this comparison also reminds us is how little the Mac OS or, indeed, Windows has evolved since reaching a design plateau in the mid-1990s. What we're seeing now is that the iPhone and smartphone market as a whole have now reached that same point – and far quicker.

On one level, the fact the smartphone hasn't fundamentally changed since 2007 is testament to the quality of its design; it hasn't needed changing. But its very success has created resistance to change – not least muscle memory and massive installed bases that don't want to have to relearn basic tasks. Apple perhaps missed a trick by not creating a successor to the traditional iPhone 8 design – iPhone 9, if you will – to launch alongside its new iPhones.

What will ultimately supersede the smartphone is not one single device, but the decentralisation of our digital lives

This inertia to change leaves the smartphone open to disruption, just like the PC before it. The smartphone is not going to disappear, of course – we still use PCs after all – but will soon no longer be our primary digital device. Apple has long been asked where the next iPhone is coming from, and the question is now being asked of the whole smartphone industry. But I would argue that this is actually the wrong question. What will ultimately supersede the smartphone is not one single device, but the decentralisation of our digital lives.

As a device the iPhone is all about centralisation. It does everything, everything goes through it, and in many ways this is its genius. While that may remain the case, rather than rely on one digital device, we will soon be interacting with many. Some of these already exist, of course: voice control speakers, activity bracelets, smart watches, smart headphones, AR goggles and the like.

In the same way, Apple has already begun to react to a slower iPhone upgrade cycle, so it's got ahead of the game with regards what might come after. The Apple Watch has quietly become massively successful. AirPods were the must-have product again this Christmas despite not receiving an upgrade in the preceding year. And it's hard to believe that Apple's major investment and focus on AR is to be confined to the iPhone. They're clearly playing a longer game.

The cumulative impact of what comes after the iPhone could be even more profound

Up to this point any new platform or technology has required a "killer app" to establish itself. For the PC it was Office software. For the iPhone it was the mobile internet and an interface to make it useful.

These smartphone successor technologies are all currently lacking their killer app, but, as before, to ask for one is really the wrong question. Their potential actually lies in their collective impact.

We are unlikely to see any single device that is as wildly transformative as the iPhone ever again. But the cumulative impact of what comes after could be even more profound.

Apple is not alone among the tech giants in trying to pivot towards life after the smartphone, and it may be that the market will be dominated by the same companies who dominate it now. They have the advantage of unimaginable financial resources, but they are also encumbered by being tied to the status quo. So, in a strange repeat of tech history, it may be that those who end up leading the new revolution could at this very moment be starting out in their parents' garage.