The migration factor would seem to be an important part of Dustin's point—along with the idea that teens and 20-somethings are leading indicators, as they were for social networks, mp3s, etc.
(I'm typing this on a 27" iMac but would broadly define myself as part of the "specialist" group.)
Incidentally, cameras appear to be following a similar trajectory to PCs, with sales falling off in the last two or so years. See e.g. http://www.dslrbodies.com/newsviews/when-will-the-panic-star... or http://www.dslrbodies.com/newsviews/march-2014-nikon-news/ha....