The flights are not going to be cheap this time. In case you can take a very long holiday, the best deal may be to take a cruise ship repositioning from San Juan to serve as a floating hotel. Now no one has announced anything yet, mainly because the odds are the the WC will be moved. But if the WC does take place here, there will be an incredible shortage of hotel rooms in Port Elizabeth besides Cape Town and Durban.
My wife and I are planning to go in 2010, but the flights are scandalously high. I actually did my graduate research in South Africa back in 1999. I spent 4 months there and had an amazing time. I'd love for my wife to experience RSA (no chavas for me, besides her). I guess we'll have to see. I'll let you know if we're am coming out! :)