Qantas have yet to announce their B744 replacement and Airbus are aware that the B777-ER is currently the front runner. In an effort to secure an A340-600 order they are offering a significantly lower aquisition cost plus for the life of the aircraft they will pay the difference in fuel that the A346 uses over the B773. Sounds very expensive considering how long QF usually keep their aircraft.
Re the A380 order:- Dixon said in Dec 2000 ( a month after the order was announced) that "Qantas had approx 100 escape clauses in the contract so that if there were any shortcomings in performance, delivery, etc then they could get out of the deal, but it was their intention to take delivery of the aircraft". I believe that the A380 will be delivered because of the huge amount of work that has already been done in anticipation of its delivery. Boeing would have to have made an extremely attractive offer on the B747-8 to entice QF to cancel the A380 order. The other issue is that Qantas is short of capacity now and couldn't wait the extra couple of years for the B747-8 to arrive.