Maybe heatsinks sticking out perpendicular, but they won't make them like hubsinks. I can only imagine the pain in the ass it would be to lace a hub with something like hubsinks installed already and not able to remove them. No thanks.
The next step in hub motor efficiency will be using different compounds for the stator, possibly using 3d printed stators that are a single cohesive piece, instead of laminations. Where the particles are separated from each other by the bonding material, to significantly lower eddy currents.
Also using different metals, so we can get a higher saturation.
Possibly also using curved teeth and curved magnets, so we can have a higher surface area for the magnets and stator teeth faces, with the same widths which would increase magnetic force between the rotor and the stator.