If you're interested in finding out about the next version of Windows Server – which for now is named "Windows Server Technical Preview 2" – take a look at the new Windows Server Technical Preview 2 Technical Library.
This library, as with the libraries for previous versions of Windows Server, is the central location for all technical documentation about the product. All content in this library is authored by members of the Windows Server documentation team, who work closely with product team members to provide you with the most current and technically accurate content on the Web.
The initial publication of this library includes information about new features and improvements to Compute, Identity, Management and Automation, Networking, Storage, and more. As time passes and the product nears completion, this library will grow, with new content being published frequently.