Its a difficult balancing act for the Australian selectors I think - how much they pick their best available squad as of today to try and win the series, and how much they take into account the ageing profile of their team and look to manage the transition process better than, say, England have managed it recently.
For me, there is no doubt that they will retain ten of their test side in their squad - Bailey is the only one whose place is under serious threat (because whilst I note that Chris Rodgers tended to score heavily in the second dig but not int he first, he still scored heavily, which is something that Australia have struggled to do post Punter). That leaves, probably, six spaces in the touring party - two batsmen and two seamers plus a speculative pick.
Should Bailey survive? My call would be no - his first innings scores were 3,53,7,0,1 in the Ashes, which is probably enough evidence that he is just not quite good enough.
So two batsmen - I'd go for Maddinson (because Rodgers can't have that long left at the top of the order) and Marsh (who did well when he first came in to the side and could bat anywhere in the order). WHoever plays, I think Smith would be the best bet at six, possibly with Watson moving down to five.
As for the bowlers, Pattinson is more or less a certainty, with one of Bollinger and Coulter-Nile my guess, though on the South AFrican wickets you can bet they would love to have Bird available to them.
And the wild card? I wonder whether they might take a leg spinner of questionable nationality (no, not Adil Rashid...)