Will I lose my permanent residency in South Africa if I don't get a return ticket when I fly to the UK?

I have South African Permanent Residency and am in the UK to complete some business. I have a return ticket to fly back to SA in January 2015. I will need to return to the UK after that on business for a while but do not know exactly which date I will be returning to SA. I therefore would want to buy only a one way ticket to the UK for now. But someone told me that SA immigration require Permanent Residents to have a return ticket when exiting SA otherwise they will consider it to be a permanent emigration. Would anyone know if that is correct?