So far we have seen many references to Windows Blue, the next version of Windows which Microsoft is working on. Today, new job postings from Microsoft reveals some references to Windows 9, it seems Microsoft is already working on Windows 9 along with Windows Blue.
Here is the description from Bing team job listing,
Do you want to join the frontlines in one of the biggest battles we are fighting in the company? Do you want to work on the latest technology? Bing brings search experiences to tens of millions of users with over a billion page views a week. As a member of the Bing Client team, you will be joining a team that is constantly innovating in the latest technology areas by combining the best of client and services to build great customer experiences. We utilize cutting edge technologies across the stack from Bing metro application development using WinJS and HTML5, innovative features in IE10 such as flip ahead and much more! The team will be constantly delivering great products in areas including Windows 9, IE11 services integration, touch friendly devices including iPad and more. Our talented, customer-focused, team delivers these features through rapid cycles of experimentation and customer feedback to bring the best ideas to market.
Another reference was found on an employee’s LinkedIn profile,
Source: MSFT Kitchen