In brief: As part of its "A New Spirit" program, Qantas passengers will introduce new flight numbers on flights to Bangkok and London via Singapore.
Qantas' flagship Sydney-Singapore-London Airbus A380 service will be renumbered from QF31 to QF1 in March next year, with the return leg shifting from QF32 to QF2.
The Red Roo's Sydney-Bangkok Boeing 747 service, which will no longer continue on to London (passengers will transfer to a codeshared BA flight for the second leg of the journey), will be renumbered QF23 and QF24.
Those 747s will be upgraded to A380 standard inside, with the new longer and fully flat Skybeds in business class.
(Tip of the hat to the ever-detailed airlineroute.net for the GDS readout data.)