These weapons have never been available on the street and they won't be available after the ban expires.
But there might be guns that have a flash suppressor or bayonet lug. We know how dangerous they are.
I just checked my NFA class III gun store and the guns that are being used in Iraq cost about $5k, at least a 6-month waiting period and a background check. I don't think the terrorist will wait that long.
P.S. These weapons are never available at gun shows.