I agree this is quite stunning.
From what I can see, as I saw the landscape draw in, they use a combination of backgrounds and rendered terrain with Speed Trees, or at least that's what they look like. The background switches smoothly between a rendered backdrop and the mesh in the same location as it makes use of some very smooth LOD between the two.
We could probably do something similar if the content creators look at this carefully. The problem though might be with matching textures with the backdrops and background images to the foreground terrain, and the requirements of a fixed camera location.
There's a lot of other factors as well including the dynamic lighting and dynamic reflections, which we still don't have yet. The T:ANE E2 graphics engine isn't quite there still, though better than we ever had previously.
