Microsoft released Windows 8 to Manufacturing. This means the code is done and the product is now being readied to ship. The official roll out date will be October 26th, 2012.
With the release, you’ll be able to upgrade for $39.99. If you buy an eligible Windows 7 PC today, you will be able to purchase an upgrade to Windows 8 Pro for $14.99 (U.S.) through the Windows Upgrade Offer.
For more on this announcement, check out the Windows blog.