If you hover over Africa you'll notice that the steepness of the lines is much lower than the rest of the world. Extrapolating from the lines I'm guessing they'll end up at 3-4 children instead of the ~2 children that most of Asia and Europe have.

No, they will end up at 2 or below when some form of long term stability is eventually reached. The political-economic situation, from outside nations messing with to internal corruption, explain a lot about its current birthrate.

China's current investment into Africa at this time may eventually bring the economic stability to many of these area. That said I'm not sure I'd want China enforcing my long term cultural stability.

China's 'investment' in Africa doesn't benefit Africa, from what I understand. They build entire towns of imported Chinese labor and take all the money out. Last I read about it.

Right? Most countries in Africa actually show dropping birth rates. The ones going up or stable are ones with war or poor social amenities.