To be honest, the more I think of it, the likelier it is it will be somewhere in Europe, probably Western Europe. Eastern Europe has had Russia patch, Northern has had Denmark patch, there has been the Far East, the Near East/Middle East, Hungary has covered some parts of the Balkans as well. I think Africa is pretty complete, especially since Ethiopia was changed. The New World is complete as well, or at least pretty much any nation there already has a special DLC mechanic so it's unlikely it will be touched. This leaves Western and Central Europe (France, Italy, GB, Iberia, HRE, Poland?) as the most plausible next patch, shortly followed by Balkans (Greece patch?) and India (Mughals patch to follow the Persian update of CoC?), or potentially Indonesia.