If the Aussies call their bluff, then 90% of the population will switch to Bing/ddg and will be fine.
More discerning Aussie searchers - like people googling for why their spring boot app won't work behind an nginx proxy - will just use a vpn to get to Google US - and they'll be fine too.
Google's dam will be broken open and the emperor's clothes will be left a little raggedy.
There's more at stake here for Google than Australia, and Aussies play hard and ruthless at the best of times (can confirm, am kiwi).