I doubt that one of the 767's will be used for this route, since the last a/c should be leaving this fall, October?
The most likely candidate I'd say is the A321. According to Great Cricle Mapper, CPH
-BSR is 2430mi and the range of the A321 is 3000mi. The 737NG and MD
-80/90 all have too short range for this operation, and the A330/A340 seems like an overkill, to me at least.
OTOH, SK945's reasoning is interesting, would be great to see new services to both JNB
According to Swedish TV4, SAS would like to start the flights as early as late August, though I personally doubt that would be possible.