The next step will be to require background checks for all private sales and after that confiscation.
If the government is so sure that background checks are effective, then how about retroactive background checks on all the weapons purchased under the Fast & Furious program that were given to the Mexican drug cartels!
Private transactions will take place outside the show and I would expect that ATF agents will be monitoring shows with security cameras and track/follow those exchanging phone numbers to their vehicles to identify them for future harassment. A good reason to have those not already paranoid about government snooping become so.