I've considered immigrating on many occasions & with relatives in Australia, England & Portugal i'm spoilt for choice. But as you highlighted, if everyone that can make a difference to change the country leaves, what impact will that have on the future of the country? We have a major brain drain issue in this country, particularly with Australia, Canada, NZ, UK & USA. Although a lot of people do come back as it isn't all its cracked up to be. Middle to upper class South Africans enjoy a very high standard of living which certainly can't be achieved in certain developed countries.
The main reasons for people wanting to leaves ranges from crime to looking for better opportunities due to affirmative action which really hasn't helped this country at all. The recession has really hit us hard but we haven't felt it as had as european & north american countries, we still continue to live on money that isn't ours & spend like math morons. For me, the biggest determining factor is the government. They still haven't done much to curb crime, they still haven't focused on improving education especially for the uneducated black majority simply because the black majority wins votes & that gives them controlling power. There's rampant corruption in the government with reckless spending the norm, ministers living the life of luxury with several homes spread across the country, more than 20+ luxury at their disposal, holidays at posh destinations flying first class at the cost of the law abiding, tax paying citizen. Fuel has risen to an all time high, we are being taxed for every damn thing & with the introduction of a highway toll tax it's driving up the cost of living.
If i were to move abroad id have to consider how easy it easy to assimilate, is english the medium of instruction in that particular country, am i willing to learn another language? South Africa is a pretty cosmopolitan country & i've been exposed to a wide array of different cultures & nationalities, so i'm not afraid to socialize with people of different ethnicity. I have lofty ambitions business wise & there are a few select countries that give entrepreneurs like myself the freedom & assistance to grow & make a positive contribution to the economy.
My number two choices are Australia, i have many friends living there along with family. Australia is pretty much a more organized version of SA with less blacks.

There certainly wouldn't be a culture clash for me at all, we love the same sports, we love the same activities along with being common wealth buddies. USA is another possible destination, again i have many, many friends spread across the country in but most of them in New York, LA & Miami. USA is an entrepreneurs wet dream, the limit really is the sky, you can make money on any damn thing plus people aren't as conservative as South Africans.