I don't think a winter league is a fait accompli. I suspect this 'hybrid season' will be a decisive factor of whether season will move. However, your timeline looks right with the Australian Cup final having been hinted as mid-November..
The 2022 season then becomes interesting. If it does become a winter league will there be expansion and a true home and away? A 26 round comp whether there is expansion or not (given 2022 FIFA dates which may change) and given a World cup in November 2022. It could start in late February - early March pause on FIFA dates and finish in October with plenty of time before the FIFA Release date of 14th November for the World Cup.