Additive manufacturing may be used to help with signature control to help soldiers avoid detection while communicating. This may take the form of printable “plastic antennas” or brain-to-brain communication via EEG with sensors on helmets that detect non-verbal movement.
3D printing may also be used for advanced robotics, where self-replicating robots can go to unsafe locales (radioactive environments, etc) where you wouldn’t want to send soldiers. These robots with a suite of sensors, could sense it’s environment and print robots to collect artifacts of these environments.
This may seems far fetched, but some of this technology exists today, some of it is currently being investigated, and the rest may very well be explored in the decades to come!