From my perspective, terragen is only one-step close to release its true power, I had seen the procedual PBR texture and curvature function in terragen but I think If there is an ambient occlusion node as a mask will be better, because in many cases you will need to blend two object to increase realism, I had tried to find solution for AO mask for month(including screen space reprojection) but there will still be many major artifact exist by using that, I am sure bring AO node into reality will be a great help for terragen, for the current several version 4.7.15 above user had ability to export obj(force-displacement) out which means It will be procedual objects, in addition with AO node we can make terragen a run-time substance painter and environmental generator, creating realistic hyperdetailed procedual terrain and object integration, substance edition simultaneously will be the feat even blender and unreal can't do for now.