This is similar what I was going to say: disposable income, behavior; and I was going to add replacement cycle.

> If you want to predict the future, just look at what middle-class American teens are doing.

I know people love to say/write this, but I'm trying to think of a period of time where this has held up within the last century. Technology, especially today, doesn't allow it. Also, teens hop on and off of fads quicker than any age group. Teens and early-20s adults have behaviors that will all change within just a few years, along with the things they deem necessary vs nice-to-have.

That the iPad, or tablet, has plateaued (or even shrinking) may be true, but I don't think the data or reasoning supports it.