Yes, declaring them illegal would make them hard to sell. But, we are not talking about the gov't making them illegal, and we are not even CLOSE to that. This discussion has nothing to do with that, we are talking about a lawsuit. This has nothing to do with whether they are legal or not. Law suits have nothing to do with making law, and suing a manufacturer for some abstract claim has nothing to do with outlawing the possession of an item. They just aren't related, so I don't see the connection.
Not only that, but if they ever did succeed in making them illegal, that would not necessarily make them illegal to *possess*. The gov't can outlaw the import, making them more expensive like "assault rifles" of today, or they can make it illegal to buy or sell them, like California is doing with hi-cap mags...but it is a far cry before the gov't can tell you that you cannot OWN something and force you to turn it in.
I am not keen on the laws and technicalities, but I do believe that portions of our constitution protect them from taking away stuff we own (4th amendment for one) and even though I am not keen on the laws, I do know that it would be a huge step for them to make it illegal fo OWN anything you already have.