The are only three reasons I can think of how this could happen:
1) China starts creating another economic bubble, which requires huge amount of mineral resources from us to buy
2) South Africa economy actually starts exporting more goods and services (lol) than it imports
3) USA economy does something weird
Nr 1 above is the only likely scenario, so how possible that is in the next five years is difficult to say. You will have to start monitoring China's economy outputs and their supposedly economy strategy/goals for the next 5 years to have a good "feel" if the ZAR will strengthen to 1USD and below.