I agree that having the full planet with such 3D datas (obtained from photogrametry or Lidar, or from any other process) is a bit futuristic...
However it's what GoogleEarth is already doing, even if the quality and LOD are bad, it's available in Gearth for some cities or specific parts of the world.
For any simulation purpose, it is quite obvious that we need to have our world(s) populated with man made stuff.
I feel that a mix of such "real" 3D datas, cleaned and modified/optimized,
to allow some procedural calculations/propagations on them, would be the best.