Today, Microsoft announced the Windows 10 April 2018 Update, which means that it's time for everything to get updated, and not just PCs. Everything with a Windows 10 core gets 1803, including Xbox One - which is already available - HoloLens, IoT Core, and Server. The company announced today that Windows Server, version 1803 will be generally available on May 7.
You might notice that May 7 is also the first day of Microsoft's Build 2018 developer conference. It's worth noting that this is a coincidence, and the Windows 10 April 2018 Windows Update rollout starts the day after. Don't expect it to align with anything that actually happens at the conference.
Windows Server, version 1803 contains a number of new features for those on the Semi-Annual Channel. For example, it includes the Windows Subsystem for Linux, along with Server Core container images, container networking enhancements, Kubernetes improvements, and more.
For those that aren't on the Semi-Annual Channel and are on the Long-Term Servicing Channel, you won't get this update. Instead, Windows Server 2019 is in the pipeline for those users, and you can test out the Insider Preview now.