To me the "art of the possible" apply here.
Scenario 1: Zuma stay in power until 2019 and loses elections,  this is unlikely because the ANC still controls the rural vote but it will certainly be the most dangerous outcome because if not accepted, he will blame the whites for the loss and will possible start a dictatorship/civil war because of his faction's control over the Police and the Army.
Scenario 2: Zuma stays and wins elective conference for his faction, when we will have a slow descent into a socialist state.
Scenario 3: Ramaposa becomes ANC president, this is an unlikely outcome with Zuma still in power. Zuma controls the ANC's rural members/leaders in KwaZulu Natal, Mpumalanga and Limpopo.
Scenario 4: The ANC loses election and accepts the result. This is the most desirable outcome but the most unlikely because of the rural vote.
Scenario 5: We cut of the head of the snake now which will  increase the chances of the moderate ANC to govern tenfold.
Terrible options, I know.