If it sunsets, IMO, the cost of the new production rifles you are talking about won't come down much. THey will just come with the "pre-ban" configuration again. The savings will be in the high capacity magzines and folding stock catagories.
The prices of guns that will be affected are the current "used pre-ban" configuration guns that are currently limited in quantity therefore more highly priced.
Of course, I could be wrong... after all I thought NDD was "straight" until I saw him in a spider man costume and posting poetry on a professional soldier site.
edited.. TR beat me to it. Look like I was probably right, about several things in this post. LOL