Probably best to wait till the teams are announced (and how empty the stands are) but with bigger fish to fry and Plymouth keen to get a bit of revenue in a shock is not out of the question.
They were similar odds when they won at Cardiff and are in better shape now.
As there are now 4 days of heavy rain forecast in Jo'burg on just about every weather forecasting site you can find, I really do find the 4/1 on a drawn 4th test quite appealing.