As far as I am aware the new F product doesn't fly HKG-SYD and there are no plans to do so - it is being downgraded to a 2-class route over the next year or so. Are you sure about that bit? And even the remaining planes with old F not infrequently get switched out to 2-class (maybe even with regional business class). If you want to be sure of a decent F experience I'd switch the HKG-SYD bit to QF128 if your ticket permits.