i think one thing you are all forgetting that needs to be addressed is that when you take over a plot of land, it is planned to decay unless maintained. Sure, there can be very few plots available right off, due to a flood of players, but if someone is offline for a month, they will probably lose their plot, and it will become available for other players to take control of.
This will majorly help in preventing lack of available space, as ownership isn't permanent. I am pretty sure that guilds are planned to be able to build townships as well. So if a guild has 20 players, that would be 20 players sharing 1 plot of land, making the available spaces exponentially larger.
Also to note, there are going to be 3 different planets/maps. So the population of players will be further spread out than we got in the alpha, and possibly will get in the beta, depending how much the devs develope by that point.
The Map is really large, there shouldn't be any need to worry about this until around the release date.