The only reason to go into space from an economic standpoint would be when it is easier to go to a different planet, set up an artificial atmosphere (that's not to say terraform it, in this case you'd only build some kind of structure and support system to keep a breathable atmosphere inside the base), extract a great deal of material, and ship it back to earth, than it is to extract that same resource from earth. Most things for that have been becoming more favorable to space mining over time- new technology and the exhaustion of earth resources, for instance. But that's all moot because earth->orbit costs are still immense.
So, it will only become commercially viable when liftoff costs are decreased. That is, when there's commercial interest and a good method of constructing a space elevator is developed. We just need some more time with the nanotubes- we're real close now.
You know, strictly speaking it would have been possible for the ancient Egyptians to set up trade routes with north/south America. Technically feasible, yes. It didn't happen for thousands of years.
I for one rather hope we don't find ourselves looking at the technical feasibility of space exploration for a similar timescale before the political, social, and economic forces collude to make it actually happen- and I think that is not a vain hope. With the massive industrialization and population growth, things happen faster now than ever. I'm just not sure if that rule applies to cultural expansion.