I have flown on the Emirates flight from Durban 5 times now for various different routings, mainly to the east, but also twice to Europe and there are two major problems with it.
1) Its not an ideal flight, journey time wise, for European travel. It makes the journey far too long. But its great for travel to the east.
2) The current plane used is a pile of junk.
These two issues will stop alot of people using the route to Europe, so a massive number of people still fly to the dreaded Joburg to connect out of the country. These Emirates flights have been 100% full every time i have flown them, so there is clearly a good market they are tapping into.
BUT there is massive overspill.
SAA will however never offer a Durban route before any of their competitors to the UK or Europe for the simple fact that they make a good R1500-R2000 extra out you by making you connect through Johannesburg and that is money they need.
Any airline that doesnt operate in the SA realm domestically could offer it without hampering their operation. So count SAA and BA out, it makes more sense for them to continually rip us off for the DUR-JNB connection.
However, if Virgin or one of the other european carriers that dont have a domestic arm were clever, they could offer the Durban direct flight and make a large share steal. There are 4million people living in the city, plus the other 7million within 2 hours drive. Yes the vast majority are not travellers at all, but there is a market that is basically fuelling the DUR-JNB domestic route to the detriment of the consumer.
A Durban to Europe connection will happen within the next two years, but it will not be BA or SAA. They will likely only react when they start feeling the pinch locally, as i dont know anyone who likes going via Joburg