There have been rumblings about the arrival of Windows 8 in 2012 as far back as late last year, when bloggers noticed some interesting slides during Microsoft PDC 2009. At the time, Microsoft's Steven Sinofsky was pretty quiet about the whole thing, but Microsoft Netherlands has been a little more open this time: In a post titled "Windows 7 First Birthday", Friday, October 22, 2010, the final paragraph of the post is where the juicy bit is hiding
"But it will take about two years before "Windows 8 'on the market." (emphasis added).
Here's the screenshot:
Here's the full post translated using Google Translate:
Reference: Windows 7 First Birthday