While I've heard some Microsoft watchers predicting that RTM and general availability of the Windows 8.1 bits won't happen simultaneously, this is not what I have heard from my sources. While new devices preloaded with the Windows 8.1 bits will probably not be out until late September/early October, I have heard that the general availability of the Windows 8.1 bits won't be held back this time around. I think users will be able to get the 8.1 bits simultaneously or very shortly after RTM.
With Windows 8.1, Microsoft is moving to a more rapid delivery schedule with its Windows releases. Instead of delivering a "big bang" release every two to three years, the Softies are now endeavoring to roll out a new Windows release on an annual basis, from what I've heard from my contacts.
Many of the testers I've heard from have noted that the preview build of Windows 8.1 is quite buggy. Yes, it's a test build. But the number of bugs had led some of us to wonder whether Microsoft might end up going later than August with RTM. It seems that isn't going to be the case. I guess that means we should expect Microsoft to roll out lots of fixes and updates for 8.1 on a monthly or more frequent basis, as it has been doing with Windows 8 since that product launched in October 2012.
During the partner show keynote, Microsoft officials demonstrated a new potential use of the Miracast support that will be built into Windows 8.1. Officials showed off the ability to use digital ink on a Surface Pro and to share handwritten notes across Windows 8.1, Windows Phone and the TV/Xbox -- using a Miracast-enabled Surface Pro as a digital white board, in effect.