JNB is my most regular long haul route (just coming up on 56 years since my first flight there) and we have booked for the end of next March for a family reunion.
Scientists currently saying it will take 2 or 3 weeks to analyse Omicron and can then say what the risks are. Currently South African medics who are working with those infected by Omicron are saying that symptoms are not too bad. The fact that, overall, the UK has far more daily infections of Covid is not the point! There is no telling what the UK govt will do if informed that the variant IS less of a problem than first thought.
At this stage, my family and I (four of us due to travel South in late March) think that we shall have an answer in good time. For those likely to travel sooner, if you have the time to be able to sit it out? There is nowhere nicer to do so! If you cannot afford the time and the quarantine - then skip it this year.
When the pandemic first broke I said that, if I could, I would go to Cape Town and rent a small holiday cottage from friends and stay for the duration. I might still there but it would have been fine!