A Federal recall will be mandated, just as many others are done all the time for various problems in cars. People in Ohio will be given the opportunity to get the cars upgraded to run in spec. Probably the dealers will have to do it any time they service one. Still, if you live in a non-smog check state and you have it serviced by a third party you could probably keep running the car using the 'cheater' fuel injection mapping as long as you want to.
Very occasionally FedGov has taken a harder line on recalls. Honda was forced to offer every owner of their three-wheel ATV's a huge cash discount on a trade in for a new ATV, and to crush the ones acquired as they were found to be extremely unsafe.
Yeah but that was for safety. This is not safety related.