Really depends on loads and mix of upgrade requests on that particular flight.
I would say this - as a Flex Y fare type that has a big say because once status is assessed, the upgrades are done by fare type, so flex Y will win out over potentially even discount W - but don't quote me on that, I'm not fully over the algorithm). Certainly ahead of most of the punters on lower fares.
Having said that, a reminder that of course with no status, the list of upgraders ahead is going to be quite long from CL/P!, through Platinum, Gold and Silver, and those in W within those status groups.
Of course, if your partner is on a more discount fare, then the chances are going to be lower too.
So you can't guarantee your partner anything except that QF11/12 , when operated by an A380, will have more J class seats than the 787, so there's more inventory potentially for upgrade - but again the paid demand and higher status demand are crucial.
If you care to provide specific date details we can see how the flights look now to give some sort of indication of how it looks now - but things can and will of course change over the course of a month.