He probably states that because the platform at its infancy seemed to hold quite a lot of potential. Its only through years of use that concludes nothing beats a good mouse and keyboard when it comes to precision typing.Maybe it is just me, but there are a lot of non-technical people I know who don't seem to have any interest in owning a general purpose PC. I remember a roommate of mine bought the original iPhone, and he said (and yes I did roll my eyes afterwards) "What do I need a computer for anymore?"
Its probably good enough to view content or browse the web, maybe short text communication like Twitter, Facebook, etc but anything more than that, its a PITA. I couldn't even write a lengthy post + images here as fast or easy with a handheld.
Tablet/smartphone makers are running out of gimmicks as well, giving users less reason to upgrade. Screen size could only be so large and performance could only be that good before it affects battery life. If laptop/desktops could be "good enough", smartphone/tablet can be "good enough" as well and they're getting there faster.