Going by the 'business as usual, we are immune' crowd, we won't have 2nd wave, only 1st, and it will decimate the land, there won't be anything left for the virus to survive in, everyone will either have had it, or be dead.
No way can South Africa support 90-day shutdown. A 90 day shutdown will kill more people than COVID 19 itself, not to mention the state coffers will be almost dry by that time (civil servants will want to get paid for nothing) etc etc.
It can work in the US/UK because everone is getting a part of $2.2 TRILLION, and big cheques in thier bank account, if anything I think isolation will decrease by a 1-3 days, looking at the infection dropping from 80% - 1.5% today I dont think 21 days will be imposed, they is a limit to what South Africans can take.
Remember we live in country where protests and strikes are common, if this drags out any longer than it should we might see a huge revolt, the anc wont want that