We haven't had a region based of of anything in Africa or South America yet, so one of those. So many cool options for Pokémon ideas from both continents, but I must say that Africa is a bit more interesting to me. As most of the regions so far have been mostly coastal, it'd be nice to see it based around a country/countries in the middle of the continent.
I think it'd be a cool idea to make a region based on the contries and areas around Lake Victoria, having the lake in the middle of the region. That'd be awesome!