Earlier quoted context omitted.
It's very difficult to change fundamental things in your well-established, popular OS. See Windows x86/x64, see the difficulties of redesigning iOS in version 7, see the disappointed people who buy an Android hybrid and try to use it as a laptop replacement. For some reason, I have all kinds of tablets at home -- iPad Air, Surface 2 (with RT), Sony Xperia Z, ... Currently I feel that it'd be a shame if the Surface di…
Apple performed a complete, ground-up redesign of their entire iOS UI layer from drawing board to shipping product in less than a year. Evolving a platform isn't a quick or easy task. It took Google maybe 3-4 years to pivot Android into a truly effective iOS competitor, and MS took even longer to respond because they had to start again from scratch. However adding a digitiser and better keyboard support, if they ever…
Well, but that's mostly redrawing the existing widgets, it looks different, but works like how it used to work. (They added some stuff like the control center on the bottom, but they haven't really _changed_ how things work.) Also, I don't consider it to be a successful restyling (it's less straigthforward to figure out whether an icon is a button or not, and so on), but that might also be a matter of taste. What I'm trying to say is adding a digitizer to iOS does not mean that you only need to write drivers and design the hardware -- you need to change some UI paradigms. And that's hard. Windows classic desktop is now touch and digitizer-enabled in the case of Surface Pro, but the whole thing is not too useful.
Apple is in a difficult position exactly because iPad Mini is so successful at the moment. Eventually large phones will devour that market as one mobile device (large phone) is usually better than two mobile devices (phone+tablet), or at least that's my prediction. They must target the same use case what Surface is trying to target: a super-lightweight laptop replacement what can sometimes be used as a tablet but renders your old, clunky laptop mostly irrelevant.