Microsoft is making big predictions again, this time claiming 350 million Windows 7 devices will be shipped by the end of 2012. Though only recently rumors began to surface that Windows 8 will be launching this year, reportedly around October, Microsoft shifted the focus back to Windows 7 this week at a forum in Seoul, Korea.

At the forum Microsoft CEO Steve Ballmer said also that should Windows 7 fill this order, it would make Windows as a whole “the most popular single system.” This should come as no surprise, as Windows has been the most popular operating system for years, but the success of Windows 7 could have led to different consequences for the system. Launched in 2009, about two and half years ago, Windows 7’s adoption rate has grown over the past year to a strong 40 percent globally. Even early adopters were satisfied, and the system has held a continuous pull for businesses and Windows users from that point on.

The prediction seems a big number at 350 million, but the number of new devices will be lower because existing machines may choose to upgrade their current software to Windows 7. If Windows 8 launches this year the number may not reach 350 million anyway, as Windows 8 is set to push Microsoft into the tablet market with the operating system supporting tablets (a change from Windows 7).

Still, with strong adoption numbers currently Windows 7 may just prove everyone wrong. LN Balaji, president of ITC Infotech was quoted last month saying that for IT departments across the globe, the “Microsoft Windows 7 migration is inevitable.” Balaji believes that “if planned and deployed properly, Windows 7 can offer organizations a host of flexible features to improve productivity, mobility, and security,” but warns that adoption is not an easy task in any case.

With a new operating system supposedly on the way, Ballmer might seem overly confident to report such a high number of Windows 7 licenses sold by the end of 2012, but the CEO has his reasons. Namely, that Windows 7’s adoption rate has been churning along steadily, and the only true rival for it would be the not-yet-confirmed Windows 8 release in October. History tells us that launch dates do in fact change, however, so no solid predictions can yet be made as to whether Windows will interfere with… well, Windows.

On second thought, Ballmer’s confidence seems to make a lot of sense.