Don't get me wrong... I've always lambasted the pundits who seem intent on declaring the PC "dead" - that's only true for people who don't actually do any work on a computer. Mobile devices are best at consuming content or *very* light work. Only idiots would argue otherwise. But let's face it - that's the bulk of what most people actually *do* with their personal computers outside of actual work.
And I'm not saying that there isn't still a need for high-powered workstations. It's just that the market for those machines isn't nearly as big as it used to be. And I think PCs have reached a tipping point where, at least outside of gaming or specialized jobs, there's less pressing need for them to be more powerful, so I think that's also contributing to the slowing market.
Don't worry - PCs and workstations aren't going anywhere anytime soon.