We are plannig a similar trip.
We are heading to Cape Town from the US in mid-September and have found the cheapest and easiest routing as being Toronto to Cape Town on British Airways. We were quoted $6.35 per kilo + $250 dangerous good fee + $50 in documents. This rate is only airport to airport, so no customs fees, etc. are included in that price. The bikes must be crated and it will take 5 to 6 days to get there. This should total about $2K for two Sym Symbas. The lowest price for airfreight we were quoted out of the US was by Schumacher at $8500!
Apparently Emirates will take uncrated bikes, but their routing doesn't look like it will work for us. But you might check with them if you aren't heading for Cape Town.
If you search ADVRider for an inmate named Fishfund, he recently shipped to Africa by air and warned everyone away from his shipper.
Good luck and maybe we'll see you on the road, just look for two baby blue Symbas!