Windows 8.1 may already be available as a public preview, but Microsoft is at work on the finishing touches before it arrives in earnest. Apparently that'll happen sometime in October, and potentially with new PCs and tablets (including 7 and 8" ones) to form a sort of launch party. Those finishing touches include making Windows 8.1 more friendly to new users, such as including a '...' button to let them know when more options are available in the likes of Mail and Calendar. In addition to those, Microsoft is going to be cleaning up any lingering bugs still plaguing Windows 8.1 and getting software updates ready. It plans to have the OS in RTM later this month, which is pretty much the final step before everyone can get it.
An October release date for Windows 8.1 would be like a one-year anniversary of the OS first arriving, and bucks a trend where more time passes before Microsoft releases a major OS update. From the sound of things Windows 8.1 is much needed, as it adds a Start button, the ability to boot to desktop, use three apps side-by-side, and pleny of other features to allow users to stay on the desktop instead of going to the Modern UI. Windows 8.1 is a free upgrade for all Windows 8 and RT users through the Windows Store.
Source: The Verge