Windows 7 will be on 42% of the world's computers by the end of this year, a Gartner analyst predicted today.
But that 2009 edition will probably be the last of Microsoft's operating systems to be deployed to desktops en masse, said Annette Jump, a Gartner research director. Instead, organizations will opt for rival architectures -- including Mac OS X and tablets -- and roll out future editions of Windows via virtualization backed by in-the-cloud storage.
Jump credited the surge in Windows 7 enterprise installations to improvements in IT budgets over the last 18 months, which will pay off by the end of this year with a dramatic move to the newer OS.
In the U.S. business market, Windows 7 will power about 40% of all enterprise PCs by the end of 2011, compared to just 6% or so at the close of 2010.
"Migration to Windows 7 will happen really quickly," said Jump. "It's already happening at a rapid pace in the U.S."
Europe's shift to Windows 7 will be slightly slower in the enterprise, Jump added, because company budgets are tighter there. Other markets that will take longer to push Windows 7 to a plurality include Japan, where the recovery from March's earthquake and tsunami will hinder growth, and in the Middle East, where political unrest is rife.
Other metrics seem to support Jump's conclusion that Windows 7 is gaining ground, although not at the pace forecast by Gartner.
Web measurement company Net Applications -- which tracks operating system usage worldwide by monitoring visitors to some 40,000 websites -- had Windows 7 with a 28% share at the end of July, and for the first time, the decade-old Windows XP under the 50% mark.
Projections based on Net Applications' data show that Windows 7 won't exceed 40% globally until the third quarter of 2012, meaning that it's unlikely any one edition of Microsoft's OS will match the prodigious share once owned by XP.
But any way you call the numbers, said Jump, Microsoft faces a problem after Windows 7.
Many organizations will skip Windows 8, which is slated to ship next year, said Jump, citing what she called "migration fatigue" after their Windows 7 push. And by the time they're ready to move off Windows 7, other forces will be in play.
"When they're ready to migrate again, maybe in 2016-2017, many alternative architectures will be more mature, and more users will be using alternate devices, like tablets and Mac OS, and potentially saving data in the cloud," said Jump.
The Mac is already making inroads on Windows' dominance, she added, and Apple's share of new machines will only increase. Gartner forecasts that Mac OS will be on 4.5% of new systems in 2011, up from 4% in 2010 and 3.3% in 2008, and grow to 5.2% by 2015.
Jump dismissed other operating systems, such as Linux -- which she said would remain a niche choice -- as well as up-and-comers like Google's Chrome OS and Hewlett-Packard's webOS.
"To get any consideration as an alternative for a traditional PC, lighter OSes will first need to get strong positions on emerging client devices such as Web books and media tablets," she noted.
Consumers, too, have alternatives to Windows, whether in the form of a Mac or a tablet.
"On the consumer side, there's some uncertainty for Windows because when people spend their money on tablets they may not replace their PCs as quickly as they used to," said Jump. "That will negatively impact Microsoft."
For its part, Microsoft is touting Windows 8 as its operating system answer to Apple's iOS on the iPad, and has promised to ship a version of that 2012 OS designed specifically for ARM-based mobile processors.
Jump questioned Microsoft's chances there, too. "They're trying to [develop] Windows 8 on multiple devices, but that's not an easy task," she said, voicing the same concerns of other analysts about Microsoft's strategy.
"The slowing growth of the traditional PC market over the next few years, especially the slow-down in professional shipments, can't be good news for Microsoft," Jump concluded.
Both Gartner and rival research firm IDC recently downgraded their PC sales forecasts for 2011, saying that with consumer demand shifting to tablets and businesses at the peak of their latest refresh, future sales growth would shift to a more modest, if steady number.
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 e-mail address is email@example.com.