With eight dissents, I think there's a good chance SCOTUS will reverse this monstrosity. One of the dissenters really got it right by stating that the majority's "reasoning" would allow anyone injured by a juvenile driving a high powerred car over the speed llimit to sue the car's maker for negligent marketing, since that maker advertised the car's performance capability.
The big problem with this firearms litigation is that the "reasoning" of the plaintiffs could be applied in any litigation against any manufacturer of any powerful or potentially destructive machine. For example, makers of various type of kitchen knives joyously advertise their products day and night on cable channels THAT CHILDREN CAN WATCH. They all claim their knives are sharper and more capable of cutting while retaining their edges than any other knives. If a neo-Manson cult acquired a number of such weapons after watching the advertising and proceeded to butcher 20 citizens, one of the victims' heirs could argue the knife manufacturer was liable for the murder because the manufacturer "negligently" advertised its great cutting properties. Same holds true for somebody whose copyrighted work is illegally reproduced by somebody with a copying machine.
Suppose this goes to a trial and the jury calls the plaintiff's arguments horse manure. Does that set any precedent?