AA has said that premium economy will eventually be on all long-haul international, but it will first appear on the 787-9s in late 2016. So expect it to not appear on the 77W used for LAX-SYD for a few years after that. AA has not yet said which booking code will be used for premium economy, nor what the mileage award costs for it will be. In addition to all that, AA is in general very stingy with SAAver awards, so if you want to use QF points, or AA miles at a non-rediculous price, expect it to be very hard to find award seats even after premium economy is in place. (If you're happy to use AA miles for AAnytime awards, then you should be able to book it once it is available on the route.)