I think worlds are expensive and time consuming to make, especially if they are based on a new theme. They need to create specific assets for them, like African trees and plants, fake buildings to decorate the neighbourhood, maybe some special effects like wild animals or sounds, BB catalogue items, etc. If there was going to be an African world, I don't think it would have been released free, most likely it would have been part of the EP and if they scrapped such a world I think it's most likely they scrapped a whole African world and gave us a world with three neighbourhoods of different inspiration, one of them being Africa. Personally, I am not a fan of tiny neighbourhoods as there is too few lots in them and thus not enough space to make them feel complete and whole worlds.