In emerging markets, the most common "main computer" isn't a tablet, it's a smartphone, by a mile. That points directly at the iPad's huge emerging-markets weakness. A "good enough" phablet (or even just a cellular tablet since many enable phone capability outside the US) can be both more useful and cheaper than an iPad + phone (let alone smartphone) combination. That seriously limits the iPad's addressable market in a way you don't see in the developed world (where more generous budget constraints and sometimes phone subsidies change the tradeoffs).
Some friends of mine in Vietnam run a shop, in Hoi An. They make a comfortable for local standards income, but after tax rates and costs they will have about $10k a year, not to be sniffed at, but still, not amazing income. A younger sister wanted an iPhone, it was a running joke that if she bought one, she would be sleeping out in the pig sty, the 'adults' (those over 20) consider such things excessive waste of money, but she being 17 decided to spend her 3 months wage on a second hand iPhone 4. This isn't un-common, her peer group all feel the need of it. She could have had something like a Nokia 620 which has all the apps she uses anyway, for a fraction of the price and it would have the benefit of new battery life performance.
Hell I've seen shoes with the Apple logo put on them[0] there is most definitely a lot of brand power and loyalty in Vietnam and China. If they can ensure that people end up with the 'correct' Apple and not a nock off, they could do quite well. The fact that kids know how to tell the real iPhone from the fact clones is enough, as they create peer pressure for the real thing.
So yes, I can see Apple benefiting from a bunch of people in the emerging markets feeling they've 'made it' when they can afford an iPad, they still are a long way of affording a car.
So then the question is - why have a separate OS for tablets as compared to laptops? The current reason is not so much to do with the UI but more to do with management of limited resources. OS's like iOS and Android are very aggressive about preserving memory and processor cycles as a way of squeezing extra life out of batteries.
On phones that different-OS resource advantage will probably continue. But on tablets, its less clear. As the intel chips get better at low power, a tablet running a 'full fat' operating system becomes more feasible.
This is what the Surface Pro 3 shows, whatever you think of it as a device: You _can_ run a full OS on a powerful processor in a fairly thin, fairly light tablet. Not the thinnest, and not the lightest, but still it raises the question: Why do tablets need a different OS?
Microsoft are tackling that question now, I think Apple will ultimately need to tackle it as well.
Honestly I think primary reason that iOS tablets have been successful is because they have a different OS. Fundamentally iOS is far less capable but also far less difficult to use and fragile than a full-fledged OS. A tablet is less PC and more consumer electronics. And that's not a hardware distinction, it's a software distinction.
It has a great deal to do with UI.
When you learn to write an app for iOS or Android, the first thing you learn is that your app needs to be ready to freeze and save state at a moments notice, and then re-hydrate itself later, also at a moments notice. This is the fundamental difference in the OS, not the touchscreen and widgets.
This is seen in OS X when an app window appears greyed out with a progress spinner in the center. The app may start out in this state if the machine was hibernated, or it may go into this state if it is open but it fits certain criteria, like all its windows being occluded by others. When this happens, the process is killed.
Where do they get the money from?
Unless... get its hands dirty by taking control of its refurbished and older generation products for developing markets.
The percentage of income spent on such gadgets (and cell phone plans) etc. is much higher for most customers in the non rich countries (essentially OECD) but those non-rich countries have over a billion people that are willing to spend a lot of money on gadgets.
And beyond those spending a lot of there money on gadgets in non-rich countries, there are hundreds of millions that are actually wealthy even in comparison to the USA in China, India, Indonesia, Brazil, Thailand etc.. The countries economies are changing amazingly quickly. Overall many are still extremely poor but many are also as rich enough to be above median income in the USA.
I am pretty sure there are way more people above median USA income outside the rich countries North America, Europe, Japan (and go ahead and include Korea, Australia and New Zealand) than live in those rich countries.
India also has an emerging middle class, though nothing like China yet.
- hardware cheaper
- software is cheaper
- cost of ownership is cheaper (time spent keeping it working, security costs, etc)
- tend to be cloud oriented, and cloud services are often free.
All of the above applies to Chromebooks, which are laptops of course.
Tim Cook mentioned that in emerging markets iPads grow much faster and that's likely because it is their main computer.
Also I don't think Apple is too worried about a larger iPhone cannibalizing iPads. A larger iPhone would likely sell for $750 (for 5.5 inches) which is much more than most people spend on an iPad and likely carries higher margins.