We've long had the technology and means to do stuff like asteroid mining. The problems center mainly around breaking new ground with the physics and mechanics of the actual activites, and the overall cost which is the biggest by far. Space is an extremely brutal, unforgiving environment for both man and machine. Extreme differences in temperatures, tons of dangerous/lethal levels of radiation, risks of collisions with other bodies, limitations on communications (speed of light, etc)... it goes on and on and on. It's certainly doable, but doing it in a cost-effective manner with "acceptable" levels of risk is something else entirely.