It's not often that a third test is as much of a mystery as this one. New Zealand have made large changes to their lineup, changing both the opening batting combination, and also (potentially) the balance of the side. South Africa look solid, and have been a class above New Zealand, but there are still some questions.
The Basin Reserve often thrown up interesting events. It's often a place where the balance switches between batting and bowling teams throughout the day (for more info, see Batting against New Zealand at the Basin Reserve
Going on that previous information, I'd suggest that this could actually be the best test for New Zealand to abandon their 4 bowler, 1 all rounder policy (which I am generally in favour of) and return to a 3 bowler, 1 all rounder line-up.
It's really a horrible test for Flynn to make his come back in, particularly if he is playing as an opener. He has been in good form, but form means little early in the day in Wellington on a green pitch.
The players that tend to do best in Wellington are the players who come in to bat in the afternoon, when the bowlers are tired from running into the wind. As a result if I was going to bet on this match I'd look at batsmen like Jacques Rudolph, Daniel Vettori and Dean Brownlie to be the top scorers. It's also good for players who play cross batted shots well, so Van Wyk and Boucher could also do well.