My everyday laptop is a late 2010 MacBook Air, running SnowLeopard (yes, I use SnowLeopard as my everyday laptop OS, and that's mainly the reason why my late 2010 MBA is not obsolete). Also, my G5 iMac from 2005 or so, never became obsolete because of Apple updates, and it still works (Apple updates from that era have nothing in common with the current updates, focusing in bloatware, forcing the user to update, and forcing hardware upgrades).
The article writer is right about the lifespan of current Apple devices, but the reason is not the build quality, nor the device in itself. The problem is the current Apple: They design software that forces the user to update even if the user doesn't want to. This is new at Apple, in the past updating was the user's choice. If you add to this that the new Apple gets a substantial amount of its income from managing and affecting the private life of the users (which current Apple users gladly applaud -most of them either teens or with a teen-like mindset), then everything ends up in the conclusion that the writer is right, although his arguments are not the reason for the 4-year lifespan, but the new Apple, and the new users.