The report by industry research firm IDC projects a "dramatic shift" over the next four years, with Windows x86 PCs dropping from its current 35.9 percent share to slightly over 25 percent. The biggest driver of the shift is the rise of mobile devices, the new center of computing where Windows devices are not keeping up with the growth of Android and iOS units.

Android Hitting 31 Percent

The report projects that ARM-based Android devices will increase from the current 29.4 market share to the top share of 31.1 percent in 2016. IDC also estimates that Apple's devices will grow to 17.3 percent, from their current 14.6 percent.

The IDC research director for mobile connected devices, Tom Mainelli, told news media that Android's growth is "tied directly to the propagation of lower-priced devices."

But that doesn't mean that manufacturers and app developers will find Android a winner, he said. Mainelli predicted that, with dozens of hardware vendors owning some share of the Android market, it will probably be hard for many of them to make a profit. He also said that a large portion of app developers will continue to target iOS, which has a smaller overall market share but has users who are "more willing to pay for high-quality apps ."

While the IDC report sees laptop and desktop computers maintaining a steady absolute amount of the total number of connected device shipments, there will be a steady increase in tablets, and a large increase in smartphones.

Consumers, Businesses, Education

Charles King, an analyst with Pund-IT, noted that the report highlighted what is being shown by other data -- that Windows PCs are holding steady in sales, but mobile devices are booming. He cited Intel data in 2010 that PC sales were continuing at about 1 million units per day, and anecdotal observation that people are buying more mobile devices but not abandoning their computers.

King said Microsoft will continue to be "dominant in the PC space," but added that the company's overall impact will depend on whether it is successful in its current effort to become a bigger player in mobile.

According to IDC, more than 916 million units of connected devices -- PCs, media tablets, and smartphones -- shipped in 2011, totaling more than $486 billion in sales. It expects the total to move beyond 1.1 billion devices by the end of this year, and doubling to about 1.84 billion by 2016.

IDC Vice President Bob O'Donnell said in a statement that smart, connected devices are playing "an increasingly important role in nearly every individual's life."

He added that this includes consumers who buy phones that can "tap into several robust app ecosystems," businesses looking to deploy tablet devices into their environments, or educational institutions working to update their school's computer labs.

Joy Shefter: