A321 NEO's make good sense for QF.
They can dual Aerobridge board to keep turns quicker L1 & L2. Also makes premium passengers feel more important if they board through a separate Aerobridge.
Fuel burn is much reduced on the NEO as compared with current 737NG.
Containerised freight is an additional advantage.
A large number of QF crews have Airbus experience, as do engineers.
Sydney, Melb, Perth & Bris would certainly welcome additional seating capacity per movement as they are getting constrained in peak times.
Endorsement costs would be insignificant (and are quite possibly included in aircraft purchase costs) over the life of the aircraft.