Did you check their sites?
Then the main site and check software
This is where announcements will be made
I have already installed the aforementioned extensions at the environment of ArcGIS Desktop.
I would also like to know when those extensions are going to be available for the ArcGIS pro as it has already happened for the ArcHydro.
See link below:
I was searching for the ability to install Arc Hydro at ArcGIS pro and it had been found here https://community.esri.com/thread/189761-does-anyone-actually-use-archydro-for-arcgis-pro
After I found the above link I was searching for its complementary extensions (HEC GeoHMS and HEC GeoRAS) but unfortunately I still have not found anything.
I hope that ESRI is going to continue the support and the development of newer versions for HEC GeoHMS and HEC GeoRAS for ArcGIS Desktop and eventually at some point for ArcGIS pro.
Because as HEC mentions at their site ,"will no longer test and verify newer versions of HEC-GeoHMS that is compatible with versions of ArcGIS that are newer than Version 10.2.1. Newer versions of HEC-GeoHMS have been made available from the ESRI FTP site; however, these newer versions have not been tested nor will they be supported by HEC."
The same reference has been published at their site for HEC GeoRAS too.
I have a project using HEC-HMS however, as you have mentioned, the HEC GeoHMS is not available for newer versions of ArcGIS. Therefore this is to kindly ask you if you have any update about that issue. Perhaps another option to add as extension to my ArcGIS 10.5.1?