The reason why there is no Pascal Drivers is that there is Dynamic Scheduling not depending on the CPU.
Maxwell was support was relatively easy, because of the use of Static Scheduling, for execution of the divers were dispatched by the CPU, the same way as Kepler. Kepler drivers were in the core of the system, so it was easy to add even beta support for Maxwell in the web drivers.
Unfortunately, because Dynamic Scheduling is slightly different, there is no easy workaround over this in the system, and there is no Nvidia Maxwell, nor Pascal kexts in systems.
One of the ways could be that Nvidia would do this is by making static scheduling on the Pascal cards for the macOS system. It would cost some of performance of the GPUs, however.
Nvidia is not out of the game from Mac Hardware. However, if they want to be again on Mac hardware, they have to bring proper Metal drivers. Because software on Apple ecosystem will always use only this API, regardless of hardware that is used in the computers. And all software will eventually migrate to Metal.