Nah..."it ain't going to happen"
Yea, okay. Has it happened before? Yes. Katrina should be a good example.
Is there momentum for making it happen now? Yes, both party members have indicated that further gun restrictions are something that "should be" tackled. And when there is another mass shooting, you will see an acceleration.
Do I expect them to knock on doors when the laws change or treaty is signed? No. However I do expect that you'll be told to turn them in or you will be deemed a criminal. If you then take them to the range, post about your vast collection, order parts for them, etc, you may then get a knock on the door. If you use them in self defense, you will be convicted of the respective crime. If the government expands enough to check on ownership, you may receive threatening calls or letters.
So, no...I don't see door-to-door searches. However I see you being put in a position where you either curl up in the corner and be quiet about them or you will be deemed a criminal.
Enjoy, America...this is the change you voted for.