Microsoft CEO Steve Ballmer predicts that more than 500 million people will be using Windows 8 by the end of next year, AFP reports. Ballmer, who was speaking at a forum in Seoul, South Korea, also expects Windows 7 to hit the 350 million device milestone later this year.

Windows 8 was described by Ballmer as the “deepest, broadest, and most impactful” operating system the company has made to date. He promised the “best economic opportunity” for hardware makers and Metro application developers who opt to support the upcoming operating system.

Corporate and enterprise demand have boosted Microsoft’s sales of Windows 7, Bloomberg reports, following the more than half decade of Windows XP success — and inadvertently helped along by the sudden requirement to shift away from Windows Vista.

One of the reasons why Windows XP remains so popular is the reluctance to upgrade to Vista in the first place. With many legacy applications still running suitably well on the decade-old platform, there was no incentive to upgrade. Vista suffered with poor backwards compatibility and performance issues, which led to many upgrading to Windows 7 as soon as it was released.

Windows 7 shot ahead of Vista and became the fastest-selling operating system to date. According to Net Applications, Windows XP has a declining share of 46 percent, while Windows 7 has a rising share of more than 38 percent.

At the current trend, Windows 7 could overtake Windows XP in October — coincidentally the month slated for the forthcoming release of Windows 8.

Windows 8 should be an interesting and testing time for Microsoft. While the upcoming operating system will run on PCs and tablets alike, the ultrabook market is still developing — in competition with Apple’s MacBook Air – and will likely boost sales in the slimmer and more aesthetically attractive notebooks.

Gartner says more than 100 million tablets will be sold in 2012, with the figure tripling to more than 320 million tablets in 2015. The research firm estimates that Windows 8 will gain more than 12 percent of the tablet market, dwarfed by Apple’s nearly 60 percent, with the iPad.

Last week, BMO analysts cut Hewlett-Packard and Dell’s price targets, after one of its analysts claimed that “Windows 8 will prove to be a disappointment, at least out of the gate.” Analysts do not think that Windows 8 will be as successful as Windows 7 was and continues to be, and that PC sales could suffer as a result.

Having said that, if Windows 7 continues to sell hot off the shelves and overtakes Windows XP in time for an October arrival, Windows 8 could push through the expected worst of it and prove analysts wrong.

CNET