There is no commercial game made with Leadwerks either, so this is just not relevant.
Also, you can save procedurally generated maps on a server (or just their seeds), once, for instance, the user has decided to establish a colony on a planet.
If landscapes are procedurally generated, you also need to save them in order to edit them. You could easily retrieve vertex information and model positions (or placement maps) of the procedurally generated map and save it, then load this in an editor.
I am not really for the procedural generation nor for the streaming, although it can give out something nice in a game like SPORE. Else, I don't know why you would need it, especially with a 4096x4096 terrain. Even the most recent MMORPGs have smaller maps and no streaming.