According to ZDNet’s Mary Jo Foley who is an extremely reliable source when it comes to Microsoft, users will be able to download a preview of Windows 9 codenamed “Threshold” late September or early October. The final release of Windows 9 is expected in Spring 2015.
Windows 9 should hopefully bring back some of the UI lost with Windows 8. A new mini Start Menu will feature a combination of the traditional Windows Start menu along with Metro apps. Metro apps will also be allowed to run in Windowed mode on your desktop while the Charms bar will be dropped and Cortana added.