Summary of the topic
As it stands, right here & now, agreed - there are no direct benefits to private GA (or to be more precise, VFR <10,000') having ADS-B out fitted.
BUT
CASA policy is now to look after "the safety of the fare paying passenger"
AND
The world is changing whether we like it or not.
Reading between the lines, this means that there will be more onerous requirements on any traffic in the vicinity of passenger transport operations, in compliance with ICAO requirements.
The net result will be that CTAF-R will be the minimum requirement wherever PTO go, have been, or want to go. CTAF-R will rapidly transform into CTAF-T, and then to CTAF-ADSB. Note that there will still be no direct benefit to GA, except that without ADS-B more & more airspace will not be available for use by private GA except under special circumstances.
Gazing into the crystal ball, for the T28 ferry of the future, without ADS-B there would be no Mildura drop-in, no Kalgoorlie, etc
So why not take the "subsidised" fitment if it is offered?
Just my opinion, and open to look at other crystal balls