I'd put it a bit differently. We need a case that completes Miller. The basic ruling in Miller was that short barreled shotguns could be taxed, and effectively banned, unless evidence was produced showing they had usefulness in a military/militia context. They do of course, as do machine guns, "sniper rifles"(including the big .50 BMG version), semiautomatic handguns, true battle rifles and real assault rifles.
Never mind other interesting sorts of arms.
A prohibitive ruling by the SCOTUS would provide ample opportunity for citizens to demonstrate the military expediency of the short barreled shotgun.