When you think about how Principled does more by just adding it instead of the other ones, like correctly tinted metal reflections and automagical fresnel, what's the point of the old shaders?
I could be wrong here, but I think I remember hearing that the Principled BSDF shader is set to be the shader to end all shaders :)
Take it with a grain of salt, I could be remembering wrong haha!
It's certainly going to make shading so much easier and take the really technical part out of it. I'm really looking forward to 2.79 (hasn't come yet has it?) 👌
It hasn't but the Principled shader is included in the 2.78 beta builds and it's really damn awesome. The beta builds also have Denoising. Download from the first group: https://builder.blender.org/download/
I thought the same, it is essential for PBS shading pipeline but i guess if you don't care about it and have more control on the creative side with the simple ones...
the Principled shader is a way to group the other shaders into a work unit (for those who don't understand or don't want to be bothered with the tech side)...
it doesn't take (for instance) the glossy shader out of the mix but rather puts it in a useful place in the pipeline...
so the shaders get incorporated (they are always present) into the grouping
that is commonly referred to as PBR (Physically Based Rendering)...
hope this helps...
:D
From my point of view, the principled shader is meant to be integrated into a workflow pipeline, or to make more physically-accurate materials. This is good for most of the things that cgcookie users need it for, but what if you're just making something quick and simple? If I need a piece of paper in the background of my render, it would be much easier to just use a diffuse shader than confuse anyone who I send my source files to with an entire ubershader. Also, if I'm looking for something more artistically styled than realistic I might still use the old shaders. For most cases yeah, the principled shader is probably going to take over. But cycles classic might still have reign in some respects.
Honestly though I haven't tried out the shader yet. So I'll just have to wait and see.