Its a winning position and it's their match to lose. They were also in winning position against India in t-20 wc and choked so fingers crossed for South Africa. Hope both these batters lord Buvama and sasta KL Rahul (Markam lol) breaks the jinx.
I doubt they will choke now considering that they still have many capable batsmen remaining.
I wouldn't rule out the possibility tbh, there has been plenty quick collapses in test cricket history that I refuse to be believe that SA has won already — yes, it's their match to lose but possibility of catastrophe is still there.
I personally don't consider anyone except Bavuma as capable test batter in this whole squad.
If Aussies can get current pair off the crease , they'll still fancy their chances.