today Microsoft released the ISO for both Windows 8.1 and Windows Server 2012 R2 for MSDN and TechNet subscriptions.
I’ve already downloaded my and i’m creating a bootable Windows 8.1 iso to upgrade my surface pro.
My server will shortly be upgraded to R2 as well…
Seems that today will be a long night
ps. note that Windows 8.1 and Windows Server 2012 R2 are not currently supported in a production environment and System Center 2012 Configuration Manager R2 is not RTM, it means that you cannot deploy Windows 8.1 with SCCM 2012 SP1 or R2 Preview