Ann: Sydney Airport Traffic Performance February 2020, page-200

Yes. Interest-rates will continue to crawl along the bottom unless we have an extreme case where inflation runs rampant, but it is hard to see it for the foreseeable future.

As for being a monopoly, that's a double-edged sword. It is exposed to adverse regulatory rulings (airlines will drive a harder bargain post-COVID-19). Also, its monopoly status will be somewhat diminished after the Badgerys Creek airport is fully functional.