I've developed hair rendering shaders and worked with hair artists for years in the film space. We are really really far away from getting a good solution for hair. Here's 2 main reasons:
1) Not enough triangles are being rendered. Let's face it, in order for hair to look really good, it needs way more triangles than what's being done now. If you guys are impressed with Nanite, just imagine how many triangles consists of a fur'ed animal like Lion King in CG.
2) Here is what I think game devs should focus on the most. We can deal with less triangles but the shading and lighting of hair is EXTREMELY poor. Not only are they still using 2 specular lobes for hair with the simplest scattering function, but no hair is being lit by global illumination and self-shadowing ambient occlusion. Film is used to 4 specular lobes that includes the translucent pass and a diffuse layer on top of getting shadows from light sources and then getting self-shadows from global illumination.
Hair is very difficult and it's one of the most taxing features in both games and film.