This change has nothing to do with wired vs. wireless. The reason South Africans can now have uncapped internet is because, previously, international bandwidth was very expensive. However, new cables connecting Africa with the rest of the world have been going live, and will continue to go live over the next few years.

So basically, the "last mile" infrastructure, whether it's cables or wireless, was never the main limiting factor when it came to internet in Africa, but may become more important in future as demand increases.