It's been a while since I was in high school, but aren't students still required to write long-form reports? I recall writing book reports and essays about historical events. In college I distinctly remember having to write a least one multi-page document for most courses (and for virtually all courses outside the hard sciences). Most people stop there, but those continuing on to grad school (even in the hard sciences) will need to write many 5- to 15-page documents, as well as a 50- to 100-page thesis.

I don't doubt that most people will not need a keyboard most of the time, but not needing a keyboard in the house seems more likely to be the niche. The niche will be 23 to 30 year-olds who have finished school but don't yet have kids in school, and the 55's, and up, whose kids have finished secondary school. Perhaps the computer will again be relegated to the spare bedroom / home office, but I can't imagine a scenario for the majority of middle-class households that doesn't have some sort of physical keyboard.