First OneWorld carrier to operate A380 will be QF. They have announced a 501 seat config and plan to operate SYD/MEL-LAX with their first aircraft deliveries, then SYD/MEL-SIN-LHR when they take sufficient deliveries. So look for a SYD-LAX as the first QF A380 long-haul flight, but I would not be surprised if they op a few SYD-MEL-SYD flights just for crew and ground handling experience first.

Considering QF now operate their two-class 747-400's with 432 seats (66 J, 366 Y), we are only talking about an additional 69 people on board.