The way I see it, if WITS is going to be done on this leg, there are two points at which it will appear:
1. Sydney: three shows, setlist shuffling certainly makes it likely that they could introduce it as something new.
2. Auckland: first shows after the release of U2:18. "Hey, here's the new song off the compilation that's selling like hotcakes right now!"
If WITS does not appear by the end of Auckland II, I think it is safe to say that it will only have a slight chance of making the next tour and be highly likely to become U2's second single to never be performed live.
But I very much believe it will show up at some point between Sydney I and Auckland II. It's a current single, it's going to radio, people will hear it before going to the concert, U2 will know that, and they just recorded it so knowledge of how to play it will be fresh in their minds.