The flow of 'emigration' would only be two-way initially. Saying that humans can survive in low gravity is not the same as having a good quality of life. We have no idea how it would affect the heart, the skeleton, muscles, psychology, fertility. I could go on but you get the picture. The psychological strain alone could make settling somewhere like the moon a non-starter. Why live in a tin can there when you're looking at a beautiful blue marble every day?
I've pointed out ways around this with human settlement of the solar system then galaxy...firstly, in the short term timescale we're talking about
: 2030-2040 We're likely to have much more advanced exoskeletons than we have now, which have already made trial runs in Afghanistan. Secondly, nanotech by this period could solve numerous problems with wasting etc .
Psychologically, the human brain can be kept occupied in ways never dreamed of by most people in the 20th century...from interactive virtual realities both for training and socialization, to the simpler method of creating the right size crew and the right chemistry.
Long term...I suggested bypassing space travel altogether, large spaceships might be already obsolete by 2050, carrying DNA and stored humans in databanks would eliminate long duration space travel and be more efficient on many levels.