At Microsoft’s Ignite conference, Microsoft employee and developer evangelist Jerry Nixon said that “Right now we’re releasing Windows 10, and because Windows 10 is the last version of Windows, we’re all still working on Windows 10.” That sounds like Microsoft won’t be releasing any more versions of Windows 10, which is true more or less.
Windows 10 is the last version of Windows, in the sense there won’t be any major releases of Windows hereafter. Microsoft plans to turn Windows into a service, where it will continue to get updates but there won’t be any major releases. The OS has now become modular to the point where Microsoft can update parts of it individually, which is exactly what it plans to do. The next update will be in 2016, codenamed Windows Redstone, but it will still be Windows 10, and not 11 or anything else. Basically, no more Windows X releases, where X is a version number or name.
As a customer, this probably doesn’t change much. You will continue to get free updates on a monthly basis to ensure your Windows experience continues to work smoothly. There may not be big numbered releases to look forward to, but Windows itself will continue to evolve and get better.