So now that we have Microsoft's official announcement that Windows 8.1 will launch August 14, there are still more details to uncover.

Note that today's announcement didn't mention RTM (release to manufacturing) or MSDN/TechNet availability. I'm still hearing RTM is still a week-plus away (possibly on or around August 26) and that MSDN/TechNet and volume licensees won't get the RTM bits until October 18.
Why not earlier? In large part it's because Microsoft is making the Windows sausage differently these days.
We are no longer in the world where the Windows team has three years to plan, build, test, modify, and then RTM a new version of Windows. Instead, since Windows 8, we've entered a world where Microsoft is giving itself about a year to perform all of those tasks.
Microsoft takes different view with Windows 8.1 | Microsoft - CNET News