Windows Server 2016, not likely to arrive until the second half of next year, is going to shake up the way Microsoft licenses its server operating system, moving away from per socket licensing to per core. The change was first spotted by Wes Miller who is, for his sins, an expert on Microsoft licensing policies.
Windows Server 2012 introduced a great rationalization in the way Microsoft licensed its server operating system. The two main editions, Standard and Datacenter, had identical features, and differed only in terms of the number of virtual operating system instances they supported. Standard supported two VMs (in addition to the host OS); Datacenter was unlimited. Beyond that, they were identical. The licenses for both editions were sold in two socket units; one license was needed for each pair of sockets a system contained.
Windows Server 2016 makes that simple system less simple. First, it reinstates the functional differences between Standard and Datacenter editions. Datacenter will include additional storage replication capabilities, a new network stack with richer virtualization options, and shielded virtual machines that protect the content of a virtual machine from the administrator of the host operating system. These features won't be found in the Standard edition.