Although the exact date isn’t yet known, the OEM release for Windows 8.1 is likely to occur during the final week of the month. Given that the 26th of August is a Monday, it’s not impossible that this date could follow the OEM release for Windows 8 by exactly one year. OTOH, everybody hates Mondays, so the OEM release could easily fall a bit later in the week instead. But at least one source — Russian language site Microsoftportal.net — has claimed that the RTM (OEM release) date could fall as early as August 16th. In two to four weeks, we’ll know for sure!
The OEM release will be made public soon, probably during the final week of August (just like Windows 8 itself was).
What does the OEM release signal?
1. That the OS is final enough to hand over to equipment makers, who will start converting their OS builds to new images, and create the infrastructure necessary to pre-install lots of copies of 8.1 as part of their normal manufacturing process.
2. That the OS will be made available through MSDN and the Windows Store to those who wish to upgrade on a onsie-twosie basis, or for organizations that might conceivably wish to start working on their own infrastructure changes to build and distribute Windows 8.1 images (not likely to be a common occurrence, though some early adopters are likely to start digging into the newest desktop version, perhaps including some laggards who are being forced to give up on XP with the end of all support scheduled for next year).
3. That we’ll have a pretty darn good idea of what the final release of Windows 8.1 is going to look like: MS will release updates to the RTM version when the GA (General Availability) release goes public in October, but it’s unlikely to see any major changes after the RTM release gets into the OEMs’ hands.