Can the VM685 memory be upgraded later?

No, the memory is built into the camera and there is no memory card slot, so storage cannot be added or swapped after purchase. The size you order is the size the camera keeps for its whole working life. If you are unsure, choose a larger size: 64GB holds a full shift of HD recording, and 128GB holds several shifts between downloads. Once footage has been downloaded to a PC or through the Hytera MCA22 docking station, the space on the camera can be used again.