Assuming for a moment this this goes forward, it opens up a mess that might be difficult to contain as applied elsewhere.
The original suit is based on two premises. One, that a gun designed "as a battlefield weapon to maximize fatalities" should have never been "entrusted... to an untrained civilian public." Two, that all the companies involved intentionally promoted the weapon with "placement in video games and macho militaristic marketing slogans that appealed to a population of mentally unstable young men."
By that standard then just about any gun used by the military, or by extension law enforcement, could be isolated as a means to find liability by the manufacturer when used to commit any crime by anyone else. Because this is a civil matter the burden of proving point one and two is fairly low.
In the pursuit of accountability we create an odd condition.
By that standard I can prove that certain cars, in combination with how they are depicted in various video games and in combination how they are advertised (a bit of a stretch,) should not be entrusted to the "untrained" public either.
Also, by that standard I can prove that anyone killed by gang violence means going after those weapon manufacturers regardless of advertising intention or legality of product purchase. It just means changing a few definitions and applying some different reasoning to points one and two.
In other words, we have no real way to ensure this does not domino into other aspects of product liability, arguably some by the wording of any future suit but not really. It all comes down to the nature of the event, the suit, and how the jury handles both points as applied to any product.
In our efforts to reconsider gun control we may be making a very big mistake even if this is a perceived win in terms of what happened at Sandy Hook. Example, who I do not see named in the suit are those to manufactured the medications the shooter in this case was taking, nor the "psychiatrist/therapist" dealing with him.
My main concern is even if we suggest this is a big win for those who oppose gun manufactures, what is next? (And how much fallout will this win cost everyone else across a plethora of products.)