The current Australian Navy 6 Collins-class submarines are scheduled to cycle through a further Full Cycle Docking (FSD) activity and Life of Type Extension (LOTE) program until retirement in the 2040’s.
In April 2016, Australia chose to build 12 Attack-class submarines (SSK) to replace the Collins class. The Attack class is based on the Shortfin Barracuda Block 1A design (a diesel-electric variant of the Barracuda-class nuclear submarine under construction for the French Navy). The other competing options were the German Type 214 submarine (possibly building a variant), or the Japanese Sōryū-class submarine.
The Australians have already spent about 2.4 billion AU dollars towards the Attack-class submarine. The projected total was expected to be about 90 billion AU dollars. The first boat was expected to be laid down in 2023.
At least 8 (SSNK) boats are expected to be built under the new Australian-USA-UK agreement. Likely candidates would appear to be either Britain’s Astute-class attack submarine or the U.S. Virginia-class vessel. The cruise missiles for either boat should be Tomahawks.