Hi,
I came across this thread and just thought I’d mention that I’m working on CityGen3D, which is a real world terrain generator that auto heightmaps and textures terrains in just a few button clicks all within Unity Editor.
It can also generate roads and spawn other prefabs automatically based on OSM data, as well as having a tree and detail placement system.
More info at www.citygen3d.com and on work-in-progress thread here:
It’s currenty in Beta so not all the issues mentioned in this thread have been solved yet (re world streaming, etc), but it’s already quite a powerful tool.
Hopefully on Asset Store later this year but Beta already available via website.