Establishing a colony on Mars would be very difficult, not because of technology but because of the costs. The cost of building space docks, space stations and space ships. The cost of mining the required materials to build a habitation structure. The cost of all the food rations and oxygen that would be needed to get started. It might never pay for itself. Earth will never have a real overpopulation problem; there is room for everyone if we all live sustainably and don't pollute the environment. Space travel will never be driven by the need to find a place to live. It might be driven by personal and scientific curiosity at first.