Not sure there will be a big change there, because they are already powerful enough for most common tasks since several years now. And everyone owns at least one phone or tablet already. So I don’t think that number is going to rise significantly anymore. Those people who are OK with using a phone/tablet for everything probably already do so right now. Maybe if living conditions for the non-super-rich become worse and people look for more affordable computing devices. But even then, older devices which can run Linux desktops for example are already dirt-cheap. I just don’t think that the UI/UX of phones or tablets is on par with desktops or notebooks running a regular desktop OS when using a big screen. Those UIs are primarily made for touch and for smaller screens. Trying to do everything with just one UI paradigm just leads to Windows 8 ugliness.