The weapons on their list are pretty scarce in the list of weapons used in homicides, compared to many others. Which means if they are successful in resurrecting the AWB nonsense of the '90s (which was also ineffectual), the lack of difference in murder rates might spur them to take action against other firearms.
When you get right down to it, the problem the big cities are having is a result, not of guns, but catch-and-release prosecutors who let violent criminals loose to ply their trade.