Windows 8.1 & Windows Server 2012 R2 have gone RTM (Release To Manufacturing). The General Availability date is 18 October but it looks like you won’t be able to get your hands on it before then even with a TechNet/MDSN subscription.
Why bother trying to keep up to date when Microsoft pull stunts like this. All other new versions of Windows as far back as I can remember have been made available on TechNet and MSDN within a month of RTM.
Announcing RTM and then imposing nearly 2 month delay on making it available to the technical community won’t win many friends.