Esri seldom share this information ahead of time, unless it is maybe a couple or few days away. That said, one can make a reasonable guess now that ArcGIS Enterprise has jettisoned support for the ArcMap runtime and ArcGIS Pro has a more frequent release cycle. Since ArcGIS Enterprise contains the ArcGIS Pro runtime, the releases of ArcGIS Enterprise seem to be getting closer to releases for ArcGIS Pro. I suspect April release, May at the latest.