Good news! Microsoft has finally unveiled the Release to Manufacturing edition of Windows 8.1 to Technet & MSDN folks. Couple of months back, they released Windows 8.1 Pro and Enterprise free previews. Release to Manufacturing build is more closest copy to final issue of Windows 8.1 which is going to be released officially on 17 October, 2013.
Windows 8.1 RTM Goes Official For Technet & MSDN Users
To download the RTM edition to your hard drive, you need to be the subscriber of any one portal; MSDN or Technet. This is essentially the Windows 8.1 and Windows 8.1 Pro bundled in a multiple edition Windows 8.1 RTM ISO file. These ISO files are available in two variants; 32-bit and 64-bit. Windows 8.1 Enterprise RTM would be released soon on the both the portals. Along with Windows 8.1 RTM, Microsoft has also made Visual Studio 2013 RC, Windows Server 2012 R2, .NET 4.5.1 available.
This RTM build is the close indication that there will be no new feature added to the Windows 8.1 now and only the stability fixes will be done till the release of stable copy. It also seems like they have taken a lesson from Windows 8 and now fixed everything to give you the Windows 8 which you were expecting exactly.
You can download the RTM builds from following links:
Get Windows 8.1 RTM [MSDN]
Get Windows 8.1 RTM [Technet]
Enjoy the RTM build!