What about improving the terrain generation? Multiple layers of heightmaps would bring so much more detail, different biomes like mountains and deserts/steps and maybe a sea? Other shaders, optimally POM shaders on near terrain or even dx11 tesselation?
Maybe the following is a bit of an enormous suggestion but if you plan to keep procedural generation ingame, what about using smaller cells for terrain and using a hash based generation system so you can generate the cells near the player on the fly at runtime and save their seed? As I said this is a bit of a question but it is possible and was often done before;)
So terrain improvement, shaders, generation, that would be fantastic!
Definetely a bit of an huge example but I'm actually referring to this: http://forum.unity3d.com/threads/24-hou ... mo.218650/
Of course all tuned down, this is not supposed to act as a game...