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.