unfortunately, what i'm gathering from these articles is that it will indeed be a single player game, simply because if you and a friend start playing (say on a server) and start evolving, let's say you two have begun a city and someone new joins.. they'll be really far behind :/
i'm not too sure how it'll work, maybe they'll find a way, but i suspect it will be single-player only..
it also seems to be designed as an "open-ended" game, meaning there are no clear objectives, just be the strongest that survives..
sounds fun because of the amount of features that exist for u to modify, but it also means there wont be much of a "mission" to set u against because existence of clear-cut objectives would cause you to focus on achieving that rather than being open-ended and "fun" in a lego-clay building sort of way
not sure i'm explaining this very well, but that's what i feel from reading and seeing this