The government cannot pull the plug on the SSR radar system if its replaced by current ADS-B technology that is insecure/spoofable/easily attacked by terrorists. I expect some to be decommissioned but grand plans to do away with SSR are a fantasy. The fundamental insecure design of ADS-B is a terrible mistake, this technology needed to have encryption built into it from day one.

A large problem with the USA ADS-B infrastructure for GA and sports aviation is the dual link layer silliness. There are likely to be many areas where say drones operating at low altitudes would be outside ADS-B GBT (ground based transceiver, the ground stations that do the ADS-R relay between UAT and 1090ES link layers) coverage so if a drone is on UAT then a GA aircraft say with a Trig ADS-B receiver won't see it, or a glider with a PowerFLARM won't see it, and so on. One possible thing would be to require all drones to transmit and receive (and relay that traffic data to the operator) on both UAT and 1090ES link layers. Seems too late to mandate dual-link receivers and/or transmitters for GA etc. within the proposed time frames. I expect the required area of carriage for at least ADS-B data-out for GA etc. to be increased, no way they can avoid that long term if you want drones to avoid aircraft. No idea if this will lead to mandatory ADS-B data-in carriage for GA.

Meanwhile you still cannot even install ADS-B data-out in a (certified) glider or GA aircraft without a STC and an expensive TSO'ed GPS. All a complete mess...

Darryl