It would be a good start if the Principled shader could be imported with some degree of fidelity. A lot can be done with just that one..

Can't happen without parity, or at least mapping between Unity and blender rendering engine.

Materials is complicated enough that they should probably not attempt to port. Unity ships with real time rendering features that blender doesn't have, so anyhow stuff will be fine in unity itself. It leaves blender plenty useful for mesh modeling, uv mapping, rigging and animation.