I can see benefits for SAR with ADBS because the GPS history will be sent to a central repository. Should make finding lost planes a lot easier and more reliable.
Also, ADSB receivers are becoming so cheap everyone can have a form of TCAS.
The old Narco Mode C transponder in my plane has failed and needs to be replaced and i don't think going to ADSB will cost anything extra.
It's a pity the mobile 5G network wasn't available a few years ago. Could have broadcast ADSB packets on the 5G network and Airservices wouldn't have needed to run base stations.