This first half hour of play will go a long way in determining who takes the momentum going into the 4th innings: whether the Saffas can take these last two wickets cheaply, or if the tail of Starc/Lyon/Hazlewood wag.
If Starc/Lyon/Hazlewood can score at least another 32 more runs between themselves, I think that target of at least 250 will psychologically dent the Saffas. They would have to exorcise the demons of their past to chase down that total in a final.
Before day 3 commences, I feel the Aussies do have the upper hand given they've got runs on the board in a low-scoring, bowler-friendly test, with the ball seaming since start of day 1.