I know people who have an iPad but not an smart phone or laptop.
I have been seeing a lot of pieces over the last few days interpreting the plateau as some sort of failure, which I find rather perplexing since what it probably represents is simple saturation and a good device lifespan.
There seems to be this almost pathological obsession with constant rapid growth and if something is not on the way to dominating it is somehow failing, usually based off people looking around at others like themselves and considering that the only 'market that matters'.
But in the real world there is more than one type of consumer, more than one use case, and as long as there is enough of a user base to keep production costs reasonable then the segment that is best served by tablets is served by them and the device succeeds. The only time this really breaks down is when the market is small enough that it pushes production prices up like we see with, say, monochrome cameras. The people they work well for love them, but there are not enough such people to keep costs reasonable, so they are commercial failures. On the other hand, DSLRs in general have not 'failed' even though they sit between cheap but goodish smartphone cameras and pricy but awesome MF backs, yet sales have more or less plateaued since they are not exactly 'replace every year' devices.