Microsoft will also release Windows Server 2012 R2, Windows System Center 2012 R2 and the latest update to Windows Intune on Oct. 18, the same day Windows 8.1 will be released.
Previously, Microsoft had said only that it would wrap up work on Windows 8.1 late this month and produce an RTM (release to manufacturing) build.
What's still unclear is whether Microsoft will make Windows 8.1's RTM available to MSDN and TechNet subscribers before Oct. 18.
Microsoft hopes that Windows 8.1 sparks interest in its operating system. Users have shown little interest in Windows 8, which at the end of July accounted for about 6% of all copies of Windows used that month to go online, according to metrics firm Net Applications.
Microsoft did not clarify when Windows 8.1 would be available on MSDN and TechNet.