There is a reason why Physx isn't used in most games.
Physx is proprietary NVIDIA solution. It would instantly degrade the game for all xbox players and AMD Graphics card users.
Not to mention Frontier would need to presumably cough up some money to NVIDIA.
Its as good as dead as far as gaming is concerned, only a handful of titles have used it in the last few years.
Great reason not to use it, independence all the way!!!