Will the ailing PC industry ever hit bottom?

Predicting the death of the creaky, old personal computer is a favorite pastime for tech pundits -- and with good reason, given the ill health of a product that once defined an entire industry. 

PC sales fell 10 percent between 2012 and 2013, according to market research firms IDC and Gartner. That decline comes on top of the hit the computer business took during the recession, when consumers and businesses slashed their spending on technology. Holiday sales were also bleak for PCs, with a 7 percent year-over-year drop over the last three months of the year.

One factor, more than any other, has accelerated the decrepitude of the multi-billion dollar industry. The reason? Mobile. Smartphones and tablets have lured people away from PCs, combining the functionality they need with the convenience that laptops and desktops can't match.

Even sales of Apple (AAPL) PCs -- until recently an object of desire for tech users -- were down more than 3 percent for the year. Hewlett-Packard (HPQ) unit sales was down by 8.5 percent. Acer, which focuses on low-priced systems, was down 28.5 percent and fell off the list of the world's top five vendors.

In fact, the only companies that sold more PCs last year, Lenovo and Samsung, did so on the basis of increased sales to businesses and because of growing demand for new products like Chromebooks (Internet-centric laptops that use Google's Chrome operating system).

The question now is how much further  PC sales will fall. According to IDC, global sales will decline in 2014, but by a smaller amount, and eventually stay flat at roughly 300 million units per year.

Some take this to mean that the real threat to PCs is over and that they're here to stay. That is likely true for the foreseeable future to some degree. Plenty of businesses and consumers have computing requirements that, at least for now, go beyond what can easily be fulfilled on a tablet or phone screen.

Yet analysts have been taken by surprise before. In 2011 and 2012, IDC and Gartner both had to lower their projections as PC sales fell off faster than expected. What will ultimately spell the fate of the computer is a factor that is difficult to discern: How many people actually need a PC.

As the power of mobile devices continues to increase, users may turn to tablets that can also display on a larger external monitor. At that point, PC's greatest strength -- the visual real estate they offer -- would vanish.