InterSystems is currently verifying InterSystems IRIS 2019.1 with Windows Server 2019. This work is scheduled to complete by the end of January 2019. In the second half of this month InterSystems will add Caché/Ensemble 2018.1.2 to be verified on this platform.
As we get closer to the completion of those tasks, I will update this post with information on release dates, and which products and version will support Windows Server 2019.