AUSPAR is not an AEGIS its just radar (AEGIS is a combat system with the SPY-1 radar) and AUSPAR has not been plugged in with the ANZAC class combat system (9LV). That radar is CEAPAR which is the basis for AUSPAR but they are very different.
There are some people within Defence looking at the ANZAC replacement. It is not so far out that it will be a science fiction boat. The ANZACs will need replacing from around 2025. Certainly one very senior defence shipbuilder I spoke to once was of the mind that the F-100 hull provided a range of options for the Navy after the AWD project as it currently stands.
The late building of the two extra Rivers and the two extra Adelaides was never a planned intention by the RAN. The last two River DEs were built, along with the upgrade of the Daring class DDs, because the DDL program had been delayed by the Government. The last two Adelaides were built as a way of transforming the naval shipbuilding industry from a state owned enterprise to AMECON, later Transfield, later Tenix, later BAES.