Predicting Windows 7's usage share post-Windows 8 is risky, but Net Applications' numbers provide some clues.
If Windows 8's update is similar to Windows 7 -- Microsoft's most successful operating system ever, the company has crowed -- the new version will accumulate about 17% of the world's OS share in its first 12 months. Much of that increase would likely come from Windows XP, which is nearing its end of life.
Under that scenario, Windows XP would cede 10.6 percentage points to Windows 8 gains, while Windows 7 would slip 5.7 points by September 2013.
But if Windows 8's uptake is more like Vista's than Windows 7's, the picture would be different: Vista accumulated an 11% share in its first 12 months.
Because XP is nearing retirement -- Microsoft will stop serving XP security updates in April 2014 -- it's possible that its decline will remain at the current average, which translates to a fall of 10.4 points over 12 months. That means Windows 7 would remain flat, more or less, as XP is the sole victim of PC replacements running Windows 8.
Things could go even worse for Windows 8, of course: XP users abandoning the aged OS could keep choosing Windows 7 almost exclusively. That's what is happening in many corporations now, and if the experts are right, the trend will continue.
In that case, Windows 7's share could actually increase after Windows 8's launch later this year. Depending on the uptake of Windows 8 and whether XP's decline accelerates, as seems likely, it's possible that Windows 7 could continue to gain share, perhaps to the tune it has over the last 12 months. That would put Windows 7's share at 57.7% by the fall of 2013.
If that happens, it would be a first: Typically, a new edition of Windows steals at least some share from its immediate predecessor. Even Vista, as poorly received as it was, pulled users from XP.
This worse-case scenario for Windows 8 would confirm what some have wondered, whether Windows 7 is the next XP, an operating system destined to remain the bulwark of Microsoft's business for the foreseeable future, or at least until the release of Windows 8's follow-on.
Net Applications' rival, Irish analytics company StatCounter, has pegged Windows 7's share at a higher number than XP's since October 2011. According to data StatCounter published Sunday, Windows 7 accounted for 50.2% of all personal computer operating systems in June, beating XP's 29.1% by a huge margin.