Have in mind that the tone and scope of ED is not empire building or large player groups/factions/alliances play. Its far more personal and (dystopian in some way), focusing on you being a single pilot thrown into the galaxy.
Player cooperation and emergent gameplay are things FD (and David Braben in particular) are excited about and want to see in the game. Having said that, its their game and their universe. This is not a democracy, nor can we as players dictate how the universe will emerge/move on. We can just influence it. Remember, systems may have billions of inhabitants, and the active players would be but a tiny speck in the totality of the universe simulation.
The point with Elite is that it's always been an open sandbox game. I think groups working towards a collective goal will be an emergent properties themselves. If enough players choose to regularly fly a particular route in and out of the core system, I want to see that route become developed automatically based on economic supply and demand, not what any one person or group think should happen.
It will be like ribbon developments along a main road, or a road into the Amazon becomes dotted with hundreds of logging outposts that slowly turn into settlements, then town and cities.
As for speed, just think how quickly this happened in America once they had the transport tech. There was a mass exodus from Europe looking for fame and fortune in to the massive expanse of America.
Now travel in ED is quick the population will rapidly spread out into a bell curve shape centred on the core systems with a large number of the surrounding system having populations of diminishing numbers of people with distance but with a very wide spread. It would be extremely odd if there was a sudden cut off with not much variation between billions of people and none!
If we were given the tech in ED now in the real world, i promise you it would only take a couple of years for there to be thousands of systems that would have dock-able outposts and settlements, and going back the my main point, I don't want FD to artificially limit this or have to spend their effort managing it when they can spend it better building us lovely new content and expansions.