Very soon there will be no users in GA to pay.So "someone" will have to pay for the essential services such as RFDS and fire fighting and maintenance of country airports.That will be tax payers and rate payers.
RFDS - donations and taxpayer now.
ARFFS - Airline pax, not GA
Country Airports - already mostly rate payers and tax payers and RPT pax if they have them.
GA pays for bugger all major infrastructure. It pays mostly for the bureaucracy to oversee itself.