I disagree completely. Why don't you write all your books on an iPad? It's not the tool for the job. In my opinion 20 years from now, assuming we don't have cortical implants or similar, people are going to go to work and sit down in front of a monitor with a keyboard and a mouse. It won't be so different to how people worked 20 years ago.
MSFT completely agrees with you. The see the Zeitgeist going towards more and more devices so they are scrambling to make handsets and tablets that no one wants to buy. They totally ignored the core desktop user with Windows 8. But this has to do with being a publicly traded company I think. For some reason a slow and steady market like desktops isn't good enough. They can't go to the investors and say "We aren't the sexy new thing, but we'll continue to make boatloads of money for the foreseeable future." (Honestly I'm not sure why they can't do that, but companies have to plan on growing for some reason.)