Microsoft wasn't kidding about its plans to speed up the Windows release cycle. Windows 7 hit stores about two years and eight months after Vista, and from the looks of it, Windows 8 will be with us some time around Windows 7's three-year birthday.
At least, so one would think after reading this press release on Microsoft's Dutch website—specifically the second-to-last sentence, which Google translates as, "But it will take about two years before 'Windows 8' on the market." (The press release, incidentally, celebrates the first anniversary of Windows 7's retail launch.)
As Engadget points out in its coverage of this story, Microsoft CEO Steve Ballmer named the next release of Windows when asked about the "riskiest product bet that [Microsoft] is currently making." Ballmer wasn't exactly very loquacious in his answer, though, so you'll have to use your imagination on this one. Considering Windows 7 did little more than smooth out Vista's rough edges, I would expect the upcoming release to bring some major new features—like some slate-friendly goodness, perhaps?