Where Will We Go After Earth Becomes Uninhabitable?

Ever since humanity discovered that there are other places outside of Earth, we've thought about leaving it. On this episode of What If we're going to do just that. But where would we go? Is building a ring world in space a possibility? Maybe terraforming Venus is our best option for a sustainable life. If we were to leave earth and create something like a ring world, where would we find the materials to do so? And if we lived on Venus, how different would it be from Earth? But before we blast off, why would we ever want to leave?