As someone who works in educational technology, I can say with confidence that tablets are going to be sticking around for well beyond 2018. Take a look at all the schools that have or are starting 1:1 programs, and you'll see that more than half of those programs are using iPads or some other tablet. Look at the OLPC tablets and what's been happening with them. Certainly there's a certain group of people who might not "get" tablets because they're not "traditional" computers, but that does nothing to discount how intuitive they can be, especially to children and the elderly. No, you're not going to be doing extensive command-line work from a tablet, but nobody is suggesting that tablets will entirely overthrow traditional computers.
Tablets are an educator's dream. You don't have to teach a child to use a mouse--they just touch what they want. Hell, you hardly have to teach any of the basic functions of a tablet to a child at all; they can figure just about everything out themselves.