I still can't envision a Government "confiscation" of weapons if the AWB were expanded to include all the "clones" as has been proposed. The logistics of confiscating would be a impossible. Even with a list of owner's names available. No one would be able to prove that listed owners didn't sell/trade/give them away. Are "they' going to arrest everyone that can't turn in their rifle? Impossible.
Few of us informed AR-15 "owners" would be stupid enough to say, "..of course officer, I'll be delighted to give you my new $1000 Bushmaster right now. I wouldn't want to break the law".
Every individual confiscation would require a court order (unless we've totally scrapped all constitutional rights by then, or Martial Law had been declared). Courts would be so clogged up that nothing would get done. Then the "appeals" would start, further slogging up the system.
...still say, will never happen. Worst case scenario would likely be, "no further transfers of assault weapons allowed after a specific future date". This would wipe out the manufacturing and sale of any new rifles.
But they would be able to manufacture replacement parts for existing rifles and not all companies would fold up. It would also create a market for parts for "kit" rifles, assembled by the owners themselves, without Government paperwork. Like "kit" cars are often made today to bypass D.O.T. safety regulations and exhaust emission requirements. Might not be as bad as it sounds...