Package talk:NVIDIA Linux Display Drivers
"nvidia-kernel-modules needs to be installed separately, this is by design for container use cases. VIDEO_CARDS can safely be removed, please do not set to VIDEO_CARDS="" as that is means something different altogether and will cause breakage."
In my experience simply installing the Gnome Stage 3 (i.e gnome-latest.tar.xz) and running "emerge -auDN @world" is not enough make available the Nvidia kernel modules, even if epro shows that you are inheriting the gfxcard-nvidia mix in. You will need to also "emerge x11-drivers/nvidia-drivers x11-drivers/nvidia-kernel-modules" before the Nvidia modules become available.