I do not think there will be any change to the backtrack rules for Africa (the backtracks being of course through Africa's northern neighbour Europe/Middle East).

Here's my thinking.

Africa has always been Oneworld's problem continent, because the alliance has so few intra-continental flights (only BA's subsidiary Comair with its small network in southern Africa) and poor connectivity to the continent from elsewhere.

In particular a swathe of countries in West, Central and East Africa only have Oneworld flights going North – to Europe/Middle East. They have no Oneworld connectivity going South to Southern Africa, or East or West out of Africa

JJ’s flights GRU-JNB will do nothing for this swathe of countries. They will still need backtracking.

(The alliance solved this problem for North Africa – by defining it to be part of Europe/Middle East! Maybe that’s the solution for West/Central/East Africa)