Microsoft has announced the launch of the Windows Server 2019 Preview. The preview build is available right now through the Insiders Program, while the full Server 2019 OS will be available in the second half of 2018 according to Erin Chapple, Director of Program Management, Windows Server. 
Chapple gives some idea of what will be new in

Source: Hot Hardware – Microsoft Launches Windows Server 2019 Preview, Full Release Due In 2H 2018