8% of US adults primarily access the Internet through their smart phone. Since smart phone usage is growing by leaps, this is likely to increase. It means that in addition to making good phones and small, cheap personal computers, smart phones are replacing some major usage of personal computers.
Consider what most consumers do with a PC:
The smart phone can do these things as well and probably at lower cost.
According to Pew Internet, 35% of US adults own a smart phone so this phenomenon can triple. Many youth will thrive on smart phones as well. Take that, Wintel, your section of the pie is getting smaller.