Zimbabwe received a raw deal from the ICC, as they got suspended and were barred from receiving funds. Do the ICC have courage to do the same with South Africa? Especially at a time when the chairman election is due? These suspensions work only against smaller boards who have small number of supporters and not against larger boards such as South Africa.
South Africa was semi-banned from playing the international cricket due to their government's racist policy (1970 -1991) so as far as banning decision goes yeah I think it's possible.