This month is not too late to repot deciduous trees, so long as they aren’t yet in leaf.
It’s probably too late for repotting deciduous flowering species such as peaches and cherries, as they have most likely flowered already, and are, by mid-late August, in leaf. Once flowering has taken place, though, they may need a trim and general tidy up to bring them into shape ready for the growing season ahead. I usually wire all my deciduous species when I check/ repot in winter, while the branches are bare.
You might also want to start working on conifers, as they can be root pruned and repotted in August and September in Sydney. Azaleas can also be repotted when they are in flower, or if they have just finished flowering, but before the new flush of growth that springs from behind the spent flowers.
Don’t forget that our annual show is on in September, so you may even like to bring trees that need a general tidy up and dressing with moss and/or pebbles in preparation for showing.
See you at the workshop!