I've also thought that this is a very plausible evolution for Apple. It just takes a few simple things to make iOS very competitive with OSX, for instance USB support, a native file browser, baked in bluetooth device support (mouse etc).
My very limited view is if I could do CAD and Photoshop on an iPad with some external input devices, that would kill the traditional desktop environment.
It's much easier for Apple to add software and hardware features to iOS than to retool the entirety of OSX to make it 'finger friendly' and with
nearly 700 million cumulative devices sold, as painful as it might seem, the sheer volume of iOS devices and active users with credit cards linked to the App Store eclipses that of OSX devices and makes it a much more sensible direction in the coming decade.