After reading the rules, I don't see any technical standards on how the system must be implemented - so it's entirely likely that the work DJI has already done

After reading the rules, I don't see any technical standards on how the system must be implemented - so it's entirely likely that the work DJI has already done on "Drone to Phone" broadcast identification can be retrofitted onto existing platforms with a firmware update as they had hoped. Too soon to tell for sure, but as somebody who just upgraded to a Mavic Air 2 this year from a Spark I am hopeful (DJI may not always be a shining example of a consumer friendly enterprise, see the SDK fiascos this year, but they don't want to piss off everybody who has bought a drone in the past few years either).