They would have to build a new frame and the mold for the frame, and the length of the operating action would have to be lengthened due to the length of the .45 ACP cartridge. Who knows what they might do in the future, but they seem to be selling every Shield they can make and their production seems to be running at capacity as they seem to be behind on pistols, making fewer revolvers, and they cannot seem to got or make enough magazines to allow customers to buy extras of the ones now in the catalog. Personally, the 9mm seems more desirable in a pistol the size of the Shield as magazine capacity will really suffer in .45 ACP. In addition, the 9mm is more controllable, allowing faster follow-up shots than the .45 ACP.