Windows Management Framework (WMF) and PowerShell 5.1 release dates have been pushed back until sometime in January 2017. Microsoft made the decision as they are still working on some bugs that affected some deployments on Windows 2016 Server.
Microsoft Blog Post
We previously announced that the Windows Management Framework (WMF) 5.1 would release shortly after the GA release of Windows Server 2016, however the PowerShell team found some issues with upgrades that could affect a small set of our customers. We are resolving these issues now, and target early January for the release of WMF 5.1 to the public.
We understand there is pent-up demand for this release. WMF 5.1 provides important enhancements over WMF 5.0, and removes WMF5.0’s need for installing WMF 4.0 first, on Windows 7 and Windows Server 2008 R2.
WMF upgrades previous versions of the Windows management stack. Upgrade code is complex, and getting this correct with WMF 5.1 has taken some time. We are close to the final bits we plan to release, but want to ensure we are able to support upgrades correctly for all of our users. As a note, learning from WMF5.0, we also feel it is important to avoid releasing near the December holiday season in the US, so that that the full PowerShell team is available immediately after we release to answer any questions that arise from the new features we have built into this product.
So, thank you for your patience. We look forward to delighting you with WMF 5.1.
The preview install files are available on the Microsoft website - Download and install WMF 5.1 Preview