The 767 has been a true workhorse for Qantas, but they are all getting old and there are better airframes which can do the same job for less fuel-burn, and less maintenance, and make less noise whilst doing it as well. Still, Qantas will be changed forever once they are all gone.
Not having followed the recent history of Qantas lately, from what I read I am assuming they will be replaced by 737s, which would presumably be NG models.
However, I can't help wondering what the state of play for Qantas would be today if their fleet had been reconfigured a few years ago to a mix of 777-200LR, 777-300ER, replacement of the 767s by 787s, and a forward program to replace the NG 737s with 737 8 Max and 737 9 Max. Probably worth keeping the relatively few A380s for a bit longer, but definitely dispose of the 747-400s...the industry has changed and what worked ten years ago may not work well enough today. The A330s came very cheaply, so work 'em hard for a few more years then sell them off or part them out. Still, such a fleet for Qantas is only a pipe-dream, sadly.