With the delay to Monday 14 July's QF29 (MEL-HKG), the aircraft is forming a delayed QF128 (scheduled 1930 hours HKG to SYD, but supposedly altered to depart at 2100 mid evening).
In theory, this allows QF30 (HKG to MEL) to depart on time as it's formed by the punctual QF127 ex SYD.
2100 hours for the 128's pushback seems optimistic as QF29 is to arrive at gate at 1929 (touchdown at 1924, and I add five minutes as a standard for taxiing but note
@tomlee1986 stating that at HKG it can take 15 minutes).