Microsoft has released a new version of Windows Server 2016 as a Technical Preview today. The Technical Preview 5 of Windows Server 2016 is available for download for testing purposes:
https://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-technical-preview
TP5 can also be found in the MSDN:
The RTM release of Windows Server 2016 is planned for the fall. A list of all new features can be found here:
https://technet.microsoft.com/en-us/library/dn765472(v=ws.12).aspx