Australian captain Ricky Ponting said there would be no let-up from the world champions despite the series having already been won after the first two Tests.
Asked whether the series win might open the door for other members of the touring squad to play in the final match, Ponting said: "I wouldn't think so.
"The guys who are in the side at the moment are playing well and deserve their selection for the next Test as well. Everyone's put their hand up and done the job."
South Africa, though, might make some changes. Batsman Hashim Amla and fast bowler Dale Steyn were added to the squad after Australia won the second Test by 112 runs in Durban Tuesday and the hosts will pick from 16 players.
Captain Graeme Smith said some of his team were feeling the effects of a gruelling programme, with the current series following a 10-week tour of Australia.
South Africa still have a three-Test series against New Zealand to play, with three matches in successive weeks starting on April 15.
"The selectors have decided to have a few extra options," said Smith. "I wasn't a part of the decision. We'll go to the Wanderers and make a decision on what is best for this Test match and for the New Zealand series."
Smith admitted it would not be easy for his team to bounce back from losses in the first two Tests. "We've been outplayed in the Test form of the game.
"With the quick turnaround time and the amount of emotional and mental strain that it takes with such important Test matches it's always going to be tough."
History is on South Africa's side. On their two previous tours Australia won the first two Tests but lost the third.
It will, however, need a major improvement from South Africa, whose batsmen have not been able to build big enough totals, while the bowlers have lacked the strike power to dismiss Australia cheaply.
"We want to put up a better performance," said Smith. "We had a terrific one-day series but we've just been outplayed on some of the days in the Test matches. We seem to get close and get ourselves into decent positions and we let ourselves down."
Smith's own poor form as an opening batsman has been one of the reasons why South Africa have struggled.
In six Tests against Australia this season, including an appearance for the World XI, his highest score was the 40 he made in the second innings in Durban.
Australian opening batsman Justin Langer will be playing in his 100th Test. He will become the third member of the current team, behind Shane Warne and Ponting, to have won 100 caps.
South Africa (From): Graeme Smith (captain), AB de Villiers, Herschelle Gibbs, Jacques Kallis, Ashwell Prince, Jacques Rudolph, Mark Boucher, Shaun Pollock, Andrew Hall, Makhaya Ntini, Andre Nel, Boeta Dippenaar, Hashim Amla, Andrew Hall, Garnett Kruger, Dale Steyn.
Australia (likely team): Ricky Ponting (captain), Justin Langer, Matthew Hayden, Damien Martyn, Michael Hussey, Adam Gilchrist, Andrew Symonds, Shane Warne, Brett Lee, Michael Kasprowicz, Stuart Clark.