The 146's would have to look pretty doubtful, as too the early 767's.
They might retain the owned 767's for freight and high demand morning and evening east coast operations.
There is also speculation that the 300's may also stay.
As far as the 737's are concerned, I would think they will all go. (Same costs as the A320 but 30 seats less)
The interesting bit is the depressed market for aircraft at the moment.
Who knows, the lessors may allow some of the aircraft to remain in Australia.