According to Paul Thurrot over at Winsupersite, the technical preview of Windows 9 will be available in October, rather than the previously rumored September. Microsoft are expected to reveal Windows 9 at an even in San Fransisco on September 30th, originally it was expected that the technical preview would be available soon after the announcement, however it appears that won’t be the case.
Windows 9 is supposed to be the unification of both Windows 8.1 (desktop) and Windows Phone, where both stores will essentially merge creating a single platform. The major change expected in the upcoming version is the merging of the new metro start screen with the classic desktop, as seen in the image below.
There are a lot more changes expected you can check out the rest of them at the source link below.