It's pretty bad although some die back from thinning acacia. Go prepared for battle.
I was keeping a close eye on this on the drive in last weekend and as we hiked the circuit of Mt Cole in Monolith Valley. We had a very tough time with acacia and port jackson mallee saplings on the approach to Talatarang a few years ago, so I was keen to see how it had developed since.
My guess is that we still have a year or two to go before those areas with tall canopy close over enough to choke off the acacia, although it is starting to thin a little.
Open mallee ridge tops will probably still be a wall of vegetation, judging from Castle saddle.
According to the fire map (
https://www.bushfirefacts.org/fire-maps.html) Holland's Gorge and the Upper Clyde don't appear to have been as burned out as some of the ridgetops, so you might be dealing more with the vegetation having naturally reclaimed unused tracks rather than ongoing effects from the fires. Would be interesting to hear from someone who's dropped in there recently.