The next version of Windows OS - to follow Vista - is known as Windows 7, and it is scheduled for release in 2009 or Q1 2010.
Here are details about it
http://en.wikipedia.org/wiki/Windows_7
Windows 7 (formerly known as Blackcomb and Vienna) is the working name for the next major version of Microsoft Windows as the successor to Windows Vista.[3] Microsoft has announced that it is "scoping Windows 7 development to a three-year timeframe", and that "the specific release date will ultimately be determined by meeting the quality bar."[4] Windows 7 is expected to be released by 2009 or near January 2010.[2] The client versions of Windows 7 will ship in both 32-bit and 64-bit versions.[4] A server variant, codenamed Windows Server 7, is also under development.
Here is another quote from the wiki article:
While officially Microsoft has stated that Windows 7 will be released by January 2010, which is three years after Vista was shipped, the company has indicated that it plans to release Windows 7 in mid-2009, in time for installation in PCs that will ship for the Christmas 2009 buying season.[36]
This article (referenced by wikipedia) does not give 2009 as a possible date:
http://www.networkworld.com/news/2008/062408-microsoft-windows7-ship-date.html?hpg1=bn
Microsoft will ship Windows 7 sometime in or near Jan. 2010, according to a letter company senior vice president Bill Veghte sent to Microsoft customers Tuesday.
The letter, sent to enterprise and business customers, will eventually be publicly posted on Microsoft's Web site.
In the letter sent to "Windows Customers" and titled "An Update on the Windows Roadmap," Veghte said "our plan is to deliver Windows 7 approximately three years after the January 2007 general availability launch date of Windows Vista."
Don't Miss!Read the latest WhitePaper - Determining the cause of poor application performanceVeghte wrote, "You have told us you want a more regular, predictable Windows release schedule" and he said that was the impetus for setting the 2010 the ship date.
Vista has been slowly gaining steam, but is still drawing fire from critics who say it has not lived up to promises.