Nanofactories enable exponential manufacturing. The first tiny lab-built device can be made to build a system with two integrated devices, which can work in parallel to build four, and in just a few months can build a full-sized nanofactory. Less than a month after that, millions of nanofactories could produce thousands of tons of products (including more nanofactories) per hour. These products will be higher performance.
Note: even if nanofactories are not produced in 20 years but only more advanced nanomaterials and improved robotic manufacturing and other extrapolations of current technology then the development trends are still heading in the direction of the capabilities of nanofactories.
The effects of more advanced technology are a lot more surveillance, stronger offence versus defence particularly with space based weapon systems. An effective deterrence is vital.