This actually makes a difference to me, as I said above. Just called the AA RTW desk, where I originally booked and bought. The agent first said that I'd have to pay up to the current price, then said that I would only have to pay to the AONE4 price in effect at the time of purchase, then said that he wasn't sure, so he would call the tariff desk.

Answer is that you have to pay up to today's fare at the point of original purchase. So, I'd have to pay the difference from the sale price AONE3 to today's AONE4, both ex-ICN. Yuck.

Looks like I'll use as much of the current ticket as gets me to LHR, then LHR-HKG-ICN will expire unused (e-ticket), and I'll have to buy one way LHR-JNB.

I'm very open to a better approach, if someone has one. Thanks in advance.