Re: fbcon driver?
Why would Nvidia use KMS? They have their own modesetting solution.
As to fbcon, there's no incentive for them to provide it. Their primary customers are all in X (and possibly Wayland in the future).
PS: In case you haven't noticed yet, the Nvidia devs don't post here anymore. They plan to open their own Linux forums, until then the way to contact them is email.