It'll be a while before QF needs to go down this road. Currently rostered hours on all aircraft and all ranks are still close to max. They can easily decrease these by about 10% without affecting the establishment. A 10% reduction in QF's ASK is a very, very large number and I think unlikely in the short to medium term.
Further, many QF crew- not A330 though- are sitting on LOTS of accumulated annual leave and long service leave. I spoke to a crew member a few weeks back who thought that his last annual leave may have been in 2005 but wasn't sure as it had been that long that he couldn't remember. I'm not a fan of handing leave back but even I have in excess of 100 days annual leave and 117 of long service owing to me. It won't be less than that by August next year due to the vagaries of the QF leave system.
Therefore there are lots of ways that excess crew can be managed in the short to medium term....especially given that QFs fleet is actually still expanding- despite what they try and spin in the media.