Microsoft is planning to unveil Windows 9, codenamed "Threshold" on September 30th at a special press event. Microsoft also has plans to release a preview version of Windows 9 for developers shortly afterwards, in late September or early October. The early technology preview will give developers a first look at the new mini Start Menu in Windows 9, alongside the removal of the Charms bar feature and several UI changes.
Microsoft is also building a combined version of Windows RT and Windows Phone, which can be seen in its press event.
Source: The Verge