Clarke's Space Elevator from "The Fountains of Paradise" is an elegant solution to the problem of getting into orbit. The advent of nanomaterials has made Clarke's vision seem far less preposterous. But the biggest hurdle to creating a space elevator is not materials science but ecomnomics and politics. Such a machine would be astronomically expensive to build and maintain, and the issue of who controls it would be non-trivial. It is not as if you could move it once constructed, and it is unlikely that we could ever afford to build more than one of them. The world will need a more powerful economic system and a more stable political climate before any space elevators can be built.
With mastery of electro-gravitics the elevator concept is obsolete.
Carbon nanotube sheets that can be used for a space elevator ribbon can also be used to make inflatable pressure-fed SSTO rocket stages that are reusable. A much more cheaper alternative that can be utilized by private entrepreneurs instead of a huge centralized project that a space elevator would be.