Considering that we have proceedural animations (walk.js) already its the direction they are going however for images it might be a tad bit more difficult to keep it balanced on the rendering engine. Technically speaking what they show there is already possible, aside of terrain and texture generation…
Complex procedural generation for textures on real time can take many milliseconds to be fully generated. (For example a simple generates rubber texture with bumps can take over 500ms per frame to be generated in substance designer.)
But if they manage it make it so that it bakes the textures in cache it is feasable, but a big challenge, but one would better utilize a suitable for specialized software to do it (be it gimp, Photoshop (norm or filterforge), blender, substance designer, etc)
Land might be simpler if its only a seed that is shared, but there are factors to be take in.