This is changing by the hour, but it would be reasonable to think that QLD, NSW, VIC will all announce border restrictions unless there is a marked change in the infection rate which is very unlikely, given all this should have been done a week ago.
Accept that airlines will not operate routine domestic passenger flights for a period until there is clear evidence that the pandemic is on the downside of the curve. At lease a month and probably more. Another 3-6 months to get up and running.
Of the 3 large domestic carriers, 2 (QF+JQ) will probably survive in a very different form for the forseeable future. The third airline (VA) will need a miracle to survive this, but time will tell how it all ends up.