Assuming we get our act together, by far the biggest breakthrough of the next fifty years will be the establishment of the first more-or-less self sufficient orbital space settlement, probably with a population of a few thousand.

This will be the most important development since life moved onto land. Indeed, it will be more important, because it will make the resources of this solar system available to civilization, humanity, and, indeed, Life itself. These resources are vastly greater than those available on Earth.

For example, the largest asteroid has sufficient materials to build orbital space settlements with a total living area over 100 time the surface area of the Earth. The huge factor comes about because a solid three-dimensional object (the asteroid) is converted into many hollow cylinders (essentially two dimensional manifolds), each a few kilometers across and holding several thousand people. Some settlements may be considerably larger than this, perhaps with a population of a million or more.