I spoke to a south african who I met on holiday about this and he said people would definitely be killed and the whole thing was a bad idea really. I hope it's all fine and nothing happens but with all those people, something probably will.
If you were a south african meeting english people on holiday, wouldn't you be doing you best to put of English people coming to your country
Seriously though, murder rates don't take into account whose murdered. Theres a high murder rate in say, LA, but a large portion of the murders are gang members killing other gang members, the murder rate amongst "innocent" people is far far lower and I'd imagine the exact same situation in South Africa. Stay out of the worst parts of the worst towns, don't walk around with a wad of cash being waved around while trying to find some weed/coke and you'll be fine, much as you would be anywhere else on earth unless you act like a tool and go somewhere stupid.
I'm happy to go to the states, have been, but I wouldn't walk around Compton late at night, theres plenty of places I wouldn't hang around in England at night, common sense = increased safety no matter where you are in the world.
I also find it laughable anyone could question how the World Cup could be held there, rewarding the corrupt, lol, the UK's got no hint of corruption anywhere has it
EDIT:- I'd also be surprised if at least one England fan wasn't killed, but I'd fail to be surprised when it turned out to be a rival football teams fan rather than a South African trying to mug someone.