All the crew that are leaving are doing so voluntarily. For most, their career is winding down and the payout conditions suit them. With several 747 retiring in the next few years, and changes to destinations they made a decision based on what suits them. No one has lost their job. Around 440 crew took the VR package. Qantas have decided that a casual work base suits them re flexibility. At the moment all the longhaul EBAs are based on a full time/part time contract, who knows what will happen when it's up for negotiation this year. Hiring casual domestic crew and transferring them to the A380 as needed obviously allows greater flexibility to the company whilst so many changes are happening. Ultimately it would work in Qantas' favour to employ everyone on leaner conditions and pay.
Like I said in another thread the training centre is booked solid at the moment with domestic-A380 conversion classes. I would think a MAM position would open up to a A380 full time position fairly quickly. 3 more aircraft coming means over 300 crew needed and the 747 crew don't want to work on the aircraft, so where does that leave the recruitment? Mam Casual.