What an asinine provision!
"Gap" is a perfect way to look at this issue. Even if the current law sunsets, there will be a similar law enacted somewhere down the road when the political pendulum swings back to the left.
Also, the AW ban sunset may permit domestic manufacturers to once again offer rifles and such in pre-ban configuration, we're still going to have problems with imported firearms.
Prior to the AW ban, the BATF was relying on its authority under the '68 Gun Control Act to screen firearms proposed for import into the U.S. - that's where the "MAK-90" thumbhole-stocked AK variant came from (to name one example), not from the AW ban. I see no reason to believe that BATF will back off from a position they've stood on since 1989 or so.