I note a whole bunch more changes to the volumetric stuff in a commit about 5 days ago. Including some stuff being renamed, some changes to defaults, ability to use a cubemap for inscattering color, support for static shadows from stationary lights. Groovy 
https://github.com/EpicGames/UnrealEngine/commit/ab9d8e35b1d136173c605a5b992631adf7985c80