Well really it depends what you mean by a colony... this is the dictionary definition, "A group of people living in such a country or area, consisting of the original settlers and their descendants and successors.". I just don't see a lunar base working like that. More likely is that it would be seasonal work much like the ISS, with workers returning to earth where their families live. I don't think we'll see any lunar colony until perhaps even past 2100. The cost of building infrastructure would have to heavily decrease, and that's not going to happen for a long time.
Beyond 2100? That seems incredibly pessimistic. Look at Bigelow Aerospace and their inflatable modules. Also, 3D printers could source materials locally. Then you have crowd-funding on the Internet, re-usable rockets, new materials, etc. etc. There are many ways of bringing down costs. This isn't the 1970s anymore!
It is perfectly feasible Wj, but I don't think there will be the wish or political means to do it. Even now there are no real permanent colonies on Antarctica for instance, and we have had the feasibility to do that cheaply for a long long time. People work on oil rigs all around the world at sea, but their families do not live with them. You first have to sort out territorial issues, and I'm not sure if that will ever be agreed upon, at least while we still have nation states like today. This is why I am very sceptical of the Antarctica section on FTL, just because it is physically feasible to live there does not mean that people will do or can do politically.
With regards to cost, where does crowdfunding even come into it. Living on the moon is still going to be prohibitively expensive compared to earth, even in 2100. The only way to form a colony in the first place would be via state sponsorship. You also have to remember that transport costs will also decrease overtime, allowing people to easily go between the Earth & Moon. Why would people live there? Why would the government sponsor families to live there? It's not as easy as simply creating a living platform, you need schools, recreational areas, hospital facilities. I can't see any nation state funding something like that.
The only reason I think Mars is a possibility is due to the distance. Transport between Mars & Earth isn't nearly as convenient or economical, any sort of base would have long term residents staying for likely over a year at a time. This could lead to a colony forming over time even if by accident.
Edited by Ewan, 09 September 2013 - 08:51 PM.