I dont think it collapsed as such though I doubt it would have lasted for decades, time was never going to be on its side . Rather it was a good example of making changes while still able to and an admission that collapse would happened if the same course were maintained. Perhaps something was learned from the Whenwes after all
I see what you're saying regarding the Rhodesians, though they far heavily outnumbered and only a few thousand fighting really.
But yes, avoiding the potential of a future war allowed for a much better position to negotiate. It is always better to negotiate from a position of strength than the other way around.
There was the real risk of the military taking over around 1994, but the retired General after meeting with Mandela decided not to go this route.
I think if had carried on and there was any potential of a collapse, then the military would have taken over.
How this would have turned out, no one knows for sure or how the whites would have reacted.
But like in a real fight, no matter how strong you are, you never know what can happen and this was probably a part of their reasoning.
Though, the military was very strong with one of the best special forces in the world.