The statements I have seen say only the “2030’s”. I have seen one write up saying these will be “second hand” boats. But by the 2030’s, the earliest Flight 1s will be entering their last years of service (coming up on 25 years).
But, I have yet to see if these will indeed be former US subs or whether they will be new builds. New builds seem to make more sense. If new builds, probably some update of the Block IV, as the Block V will have the VPM installed with additional vertical missile tubes to replace the Ohio SSGNs being retired.
The next generation SSN(X) is already being studied and preliminary design underway. It will return to Seawolf hull size ( more weapons carried), have electric drive and probably the X-stern. The latter two features are planned for the Columbia class SSBNs.
The political alliance was probably the main reason for this deal.
At that time, the Australian government thought that they will get the nuclear subs in 2040 - and would have to do something, to run or replace the Collins class until then. I.e. in the short- and medium-term, this decision weakens the Australian navy.
Is there anything new regarding the timeframe, when this subs will be available?