This analysis (which I found from here) I also think is exactly right.
And the iPod analogy is good. By the time people were even doing any catching up to the last iPod, Apple was on to the next better version, and then the iPhone which was a massive leap ahead.
But I think there's another comparison that should be even scarier for all the other big companies. What if it's like how Microsoft won the OS battle. In the late 80s and early 90s there were other computer companies, and other operating systems. I had an Apple ][gs for college, there were Macs, and Next, and Sun, and Unix, and more. Even on PC hardware there were more choices, a friend used OS/2 for many years.
In the end, Microsoft won and Windows has been the dominant consumer platform ever since, with Mac in a smaller 2nd place. (*Consumer, servers are different. But everybody I know owns a computer, and none of them own a server.)
A phone, even with no apps, is still a phone and everybody has a good reason to own one. A tablet with no apps doesn't do much. And Apple may already be to where Microsoft got with Windows. If you wanted to have lots of choices for software in the 90s and 00s, Windows was it. Which then fed to developers to make more.
Yes, a tablet may never be as good for some tasks as a computer...but it's as good or better for so many others.