I'm seeing the availability as:
J9 C9
If it stays at that, I think you have a reasonable chance.
Remember it's a 2 class plane only, so plenty of J seats. Even more seats if they substitute a 3 class plane onto the route (although unlikely due to current plane issues)
Can't you call QF and request they ask the powers that be to release the D class seat? As a WP, surely you have a good chance....