Proper promotion and relegation would be disastrous for the A-league. Many clubs that would be relegated would die or at least never recover financially to make it back to the top flight. Australia just doesn't have a P/R culture.
I see this talk as having a pseudo P/R to appease the requests from the AFC. Clubs at the NPL level will have the opportunity to be promoted if they satisfy a whole heap of off-field criteria as well as being successful onfield. They would need average crowds and membership pushing 8-10k+, annual revenue capabilities of $20m+, facilities up to A-League standards, etc .... Alternatively, clubs in the A-league that fail consistently to satisfy certain criteria will be open to be relegated to the NRL level and replace by a NPL club that has met the promotion criteria.