More and more states will adopt this because way too many gun owners support background checks.
It's a poor argument to support running a background check on a guy who responds to a local sales ad in the newspaper for a 1911 at Academy then turn around and not support a background check on a guy who responds to a local ad for a 1911 on Armslist. Or two tables at a gun show, one operated by a FFL versus a non FFL seller. Or or or....
IMO, the right approach is to fight for repeal the GCA of 1968 and do away with background checks, period. Until more gun owners reject the entire FFL system, the move toward universal background checks won't stop.