This is just the beginning of human expansion. We have a lot of this solar system to expand into. Not to mention nearby star systems. People have a limited mindset when it comes to the future because they can only see to the next election cycle. If you don't think we can leave earth and expand to other realms, go talk to people like Elon Musk. Limited resources are only limited to this planet. Energy is essentially free if we want to make the investment. All the rest of our needs for metals and other rare elements can be mined elsewhere in the solar system. Sure, we might have setbacks along the way, but the trajectory is clear and it will happen.