“He was in search of an answer
The nature of what we are
He was trying to do it a new way
He was bright as a star
But nobody understood himThere’s something he never told us
It died when he went away
If only he could have been with us
No telling what he might say”
Surface Your Real Self 
I haven’t kept up with what’s going on at the Primal Institute, but I recall that in some of his later writings he focused on the role of epigenetics in illness. Unfortunately, I didn’t understand most of the science. I’m hoping that there is a continued refinement of the Primal process and research into its results even in his absence.
On another related note, I was surprised to find out that there are similarities with the Primal process and prolonged exposure therapy, which happens to be one of the more effective treatments for PTSD. It comes down to safely re-experiencing the trauma followed by gradual present-day integration. The approach is somewhat different though.