I can't imagine South Africa will bar outsiders from entering. If anything they already seemingly have herd immunity which baffled the world and they have very few cases. The WHO speculates that people from that region might have a natural resistance to the disease.
They need the tourism dollars and I can't imagine they'll stay closed by August of next year. I plan on moving on to Thailand or Japan and not actually entering Hong Kong, but things may change depending on where you're allowed to go. This is all assuming a vaccine has any efficacy and this is just wishful thinking after being couped up for so long.