Gartner today scaled back its forecast of Windows' near future, saying that while Microsoft's operating system will power an increasing number of devices this year and next, the gains will be smaller than it projected six months ago.
For 2013, Windows' share of the operating systems on all devices -- smartphones, tablets, PCs, ultra-light form factors, and PC-tablet hybrids -- dropped 5.8% compared to the year before, an additional half-percentage point from the 5.3% the research company pegged in January 2014 for the year prior.
This year, Windows' share of the device operating system market will grow 2.3% to 333.4 million devices, the bulk of them traditional PCs and what Gartner dubs "ultramobiles, premium," or the top-tier notebooks. Windows' growth, however, will come from smaller systems -- smartphones in particular.
"Windows phones will exhibit strong growth from a low base in 2014, and are projected to reach a 10% market share by 2018, up from 4% in 2014," said Annette Zimmermann, a research director at Gartner, in a statement Monday.
In 2015, said Gartner today, Windows will power 373.7 million shipped devices, a year-on-year increase of 12.1%.
Gartner's numbers today were different than those in January, when it was much more bullish about Windows. Then, analysts projected that Windows device shipments would grow 9.7% in 2014, with another 17.5% increase in 2015. In the latter year, 422.7 million devices of all kinds were to ship that ran Windows.
Although Windows will continue to grow, Gartner's estimates today were significantly down from those it made six months ago. Most striking was the downgrade of Windows' 2014 gains to about one-third of the earlier forecast.
The revised estimates also mean that Windows will account for a smaller share in both 2014 and 2015 than projected previously. In January, Gartner said that Windows would capture 14.3% and 16.1% of all device shipments this year and next, respectively. Today's numbers put Windows' share at 13.7% (2014) and 14.4% (2015) instead.
The reason Windows forecasts were downgraded, said Gartner analyst Mika Kitagawa, was twofold: a softening of tablet shipment growth and the continued reliance of Microsoft on traditional PCs for the bulk of its licensing sales.
"Microsoft will stay in the traditional PC market," said Kitagawa.
Those systems will continue to struggle, with downturns in 2014 and 2015 of 6.7% and 5.3%; in January, Gartner said that the category would be down 7.2% this year and 3.4% next. Adding in its "ultramobile, premium" numbers, the total personal computer market is now forecast to shrink 2.9% in 2014 and grow by 2.7% in 2015.
Previously, Gartner had pegged ultramobiles to grow much faster, with the total personal computer market believed to be flat this year (0.3% growth), with a more robust 4.6% increase in 2015.
The expected increase in Windows phone shipments will not be enough to make up the difference.
Windows wasn't the only platform that Gartner said would grow slower than it had believed before: Apple's iOS and OS X combined number were also downgraded.
For 2014 and 2015, Gartner now forecasts that iOS/OS X will power 271.1 million devices in 2014 -- most of them iPhones -- and 301.3 million in 2015, for year-over-year growth rates of 14.8% and 11.2%.
Six months ago, Apple's estimated shipments were more optimistic: 344.2 million and 397.7 million for this year and next, respectively, representing increases of 29% and 15.4%.
Not surprisingly, Android will take up the slack, said Gartner, which predicted Google's mobile operating system will become even more dominant. Where six months ago Gartner projected that Android device shipments would grow by 25.6% and 13.8% in 2014 and 2015, today it modified those estimates to 30% and 17.3%, respectively.
This year and next, Android will account for 48% and 52.9% of all device shipments, Gartner forecast today, upgrades from January's numbers of 44.6% and 44.7%.
Gartner is now pegging total Android device shipments for 2014 and 2015 at 1.17 billion and 1.37 billion, up from previous bets of 1.1 billion and 1.25 billion.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is email@example.com.