By that argument Smart phone should of be displacing computers.
The reason I choose smart phones is they show a clear limitation of the form factor. It is not the power in them but a limitation of the form factor. They are more powerful than computers were 10 years ago yet due to the form factor there is a lot less than can do.
Hence the reason 10% seems pretty likely is the tablet form factor is going to be what limits its growth for the large part. It is to limited on storage, attaching other things to it.
Touch screen keyboards are good for quickly things but for anything longer it is another story. This is easy to see proof of it just by looking at people who have switch from hardware keyboard smart phone (for example blackberry) to a touch screen only one. The length and how often they write longer emails drops a lot. It becomes quick replays but they will not type out long emails any more. Same effect will happen on a tablet.
Some of us can extrapolate the current tablet capabilities forward a few years and see some extensive content creation, storage (more flash memory and cloud backup) and connection (high bandwidth WiFi and LTE plus Light Peak) capabilities. Demand driven I would say.
"This is easy to see proof of it just by looking at people who have switch from hardware keyboard smart phone (for example blackberry) to a touch screen only one. The length and how often they write longer emails drops a lot. It becomes quick replays but they will not type out long emails any more. Same effect will happen on a tablet."
Yes this will happen, but I would call the death of rambling and verbose emails a positive, not a negative. Either way, there isn't any constraint of people authoring books on tablets either, especially with connected keyboards.