Microsoft’s tablet-centric version of Windows is going to come very late to the market if the latest rumors are true. According to a report on BusinessWeek, the company expects public testing to begin at the end of this year with partners and customers, but it won't release its competitor to Apple and Google's tablet operating systems until the 2012 back-to-school season around September.

That's two-and-a-half years after the original iPad launched. By then the iPad 3 will likely have been out for a few months and Google's Android will probably be on version 4 or later, with plenty of manufacturers backing the platform. Even Palm will push out its first webOS tablet this year and so will RIM with the BlackBerry PlayBook.

A recent rumor suggested Microsoft is planning a demonstration of its Windows 8 tablet platform in July this year. Additionally, a couple of early development milestones have already been seen in the wild and an alleged Dell roadmap shows the company is interested in having a Windows 8 tablet ready for sometime next year.

We can't blame Microsoft for taking its time to ship a competitive product. After all, it's still ironing out issues with its phone platform and the next version of Windows is expected to add in support for ARM processors and improve its tablet usability. But the 'end of 2012' timeframe would concede a lot of market share to its competitors much in the way Windows Phone 7 was late to the party and is now bumping along the bottom of the market.