Just listening to an 'expert' pontificating (= hy praat kak) on 567 Cape Talk, saying that against 'all the competition' the route isn't viable as half the revenue is in ZAR. Apart from BA the competition is connecting flights via FRA ZRH AMS PAR etc, and in many cases much longer routings (e.g DXB AUH IST) or less desirable such as via ADD NBO CAI etc.
(QR have just announced non-stop DOH CPT using the Dreamliner.)