Warning: topic below can be very boring to some viewers...
I had never worked for ATO myself. So here is my best guess:
I don't think the residency test would be affected(for now). However, they would be more strict/vigilant on enforcing the residency rules. Currently even foreign employment income of >90 days is exempt, so they wouldn't worry too much if someone is say on a 1 year contract. It would be exempt anyway, especially if he/she is not claiming any social welfare payment. However, since the proposed law is mainly to generate more revenue for the government(judged by the $57 billion deficit we are having), they would scrutinize more on the length of the overseas employment contract, plus any additional proof to determine whether someone should be considered a tax resident, such as owning property in OZ, existence of close family ties etc as you mentioned.
On the other hand, for people working overseas(as per IT2650), I think they put more emphasis on the 'permanent place of abode' test. Permanent is in contrast to 'temporary or transitory', not 'everlasting or forever'. So if someone has a leased property overseas of a reasonable length(better still if someone bought their own property overseas) where he/she lives with the families and sleeps at night, they would be considered non tax resident even they still own their property in OZ whether or not they have rented it out.
Obviously we(speaking for ourselves) came to HK with one of the key reasons being the low taxes here. Of course we don't want to be caught by this. If, however, something as radical as changes to the definition of tax resident happened, we'd be moving back as fast as we could.