Hello,
Unity 5 will be using a Spec/Gloss workflow for Unity 5. It is a derivative of Disney GGX BRDF.
They will be using some different terminology as to try and help bridge the gap from traditional map creation to PBR. For instance, they are using smoothness instead of glossiness or roughness. I feel this is not the best approach in terms of keeping true to the naming conventions already used in PBR workflows, but its not technically wrong either. PBR is more of a methodology rather than a standard. The map creation principles are the same and this provides the ability for PBR content to be authored in a consistent manner. I would have liked to see Unity use the same conventions as UE4.
However, the good news is our Spec/Gloss workflow works well with the Unity 5 PBR shader. Personally, I like metal rough much better, but we offer both workflows and our shaders are using Disney GGX as well. Its good that Unity is using GGX. I believe it is a derivative of GGX where they have made some custom tweaks, so we will need to see how it goes through the Unity 5 beta cycle. I've been testing the workflow and our spec/gloss PBR maps are looking good in Unity with a 1:1 rendering parity.
The Unity 5 standard shader is using the following convention.
Diffuse RGB (Albedo)
Normal RGB
Specular RGB (Smoothness map in Alpha of the specular map)
I'll definitely be making some new PBR videos.
Cheers,
Wes