For most contract companies it shouldn't mean going down the drain - just put up headoffice or base in a different country, most aircraft and maintance is done at place of operation outside of South Africa anyway. Of course the cost of relocation might be a factor.
For operators only operating locally, it will surely mean less or no business at all. Tourists will also avoid the country - I think it will go down after 2010 when the whole soccer show is over. The global recession at this time is also not helping.