To test the release, those interested should sign up to be Windows Insiders. The final version is slated to roll out to users in the latter half of calendar 2018, right around the same time as the next feature update for Windows Server, known as 1809, which is expected to roll out in October 2018.
Windows Server 2019 is going to be the next version of Windows Server that qualifies as a Long-Term Servicing Channel (LTSC) release. Windows Server 2016 is the current LTSC release of Server.
Microsoft officials have said before that the on-premises/LTSC versions of Windows Server will include features that previously have debuted in the Semi-Annual Channel versions. In today's blog post about Windows Server 2019, Microsoft officials listed a few of the features they're planning for Server 2019.
Linux containers will be able to run on Windows Server 2019
Further reduction in size of the Server Core base image in Windows Server 2019
Kubernetes management of Windows Server 2019 hosts
Project Honolulu (Microsoft's graphical management tool for Windows Server that's been in preview) will be generally available and be able to manage new hybrid-cloud scenarios as of Windows Server 2019
Microsoft officials said they will release more information on these and other coming features as Windows Server 2019 gets closer to being available before year-end.
In this build, testers can try out "Cluster Sets," a feature designed to increase cluster node count in a single Software-Defined Data Center cloud "by orders of magnitude." A cluster set is a group of multiple failover clusters which can be compute, storage or hyper-converged.
Testers also can preview Windows Defender Advanced Threat Protection (ATP) support for Server 2019, as well as Windows Defender ATP Exploit Guard, a set of four host-intrusion-prevention capabilities.
Support for shielded virtual machines on Hyper-V hosts that are intermittently connected to Host Guardian Service is in today's build. Support for Linux running in shielded VMs (flavors supported include Ubuntu, Red Hat Enterprise Linux and SUSE Linux Enterprise Server) is there, as well.
Update No. 2: Microsoft is planning a price increase with Windows Server 2019. Its blog post today acknowledges that "it is highly likely we will increase pricing for Windows Server Client Access Licensing (CAL). We will provide more details when available." (Thanks to Directions on Microsoft's Wes Miller for the heads-up.)
Update No. 3: Microsoft also released a new Redstone 4 Windows 10 client test build (17217) to the Fast Ring today that includes a number of Cortana UI enhancements plus several fixes. Microsoft is planning to roll out Redstone 4 -- likely to be named "Spring Creators Update" -- to mainstream users starting in April.