Qantas will keep their options open for 737-800 replacement and are waiting on the NMA so they can compare it with the A321LR/XLR. Still, given how hard JQ is going on the A321, the NMA is going to have to be a pretty awesome reborn 767 to get in there. Expect Boeing to offer up a mix of NMAs and perhaps Max 10s and 8s in a package deal, maybe even with some E2s thrown in to replace the 717s.
For now though, with the other mob at least two years away (perhaps more) from touching their first Max, they can take their sweet time when it comes to narrowbodies.
More likely will be that some of the 787-8s from JQ will transfer across to QF once the neos get going in JQ and take over the runs to Bali. At that point, they might decide that JQ steps out of widebody altogether, and the -8s supplement or replace the A330s into Asia. It was always intended that the -8s at JQ would be replaced by the -9s that offer lower CASK and greater range, but the way they are deploying the -8s now tells me that the idea of longhaul low-cost dominance is out of favour.