Birth rates in Sydney where the young families are is 2.05 .. Camden, etc where the housing is affordable.

Birth rates in the inner city areas and expensive suburbs is low.

Will Australia suffer if high priced lawyers and real estate moguls are not replaced?

Yes, the birth rates are higher where the birth rates are higher, but you could do this with any city - find some enclave that's doing better than the rest on whatever metric. Sydney as a whole is below replacement fertility just like every other large westernized city, and the trend is down, not up.