You can now grab the Hyper-V Server 2016 Technical Preview 4 from the TechNet Evaluation Center
Microsoft Hyper-V Server delivers enterprise-class virtualization for your datacenter and hybrid cloud. Hyper-V Server 2016 Technical Preview 4 provides new and enhanced features that can help you deliver the scale and performance needs of your mission-critical workloads.
As a reminder, these are early pre-release builds. Many of the features and scenarios are still in development. As such, these builds are not intended for production environments, labs, nor full evaluations. This is pre-released software; features and functionality may differ in the final release.
Need more information about the next version of Hyper-V Server? See what's new in Hyper-V Server 2016 Technical Preview 4.