My concern wouldn't be finding ammo in larger cities in Africa, but finding ammo out in the bush. If you're hunting wild Africa (rather than game ranches in South Africa and Namibia), then the nearest large city may be many hours away, whether by Land Cruiser or a charter plane. Just about every dangerous-game PH has a stash of .375 H&H, whether his own or ammo left behind by clients.
I don't think the .375 Ruger is going away, but it will be a long time before ammo will be found almost everywhere.
