Caliphate? No, not likely. There were pan-African and pan-Arab movements in the 50s and 60s, and they went no where. There are many different countries, each with their own style of government (kings, dictators, elected dictators, strong-men, central military governments, control by local war lords, and a hand full of semi-democracies). The idea that the powers that be in each of these countries is going to turn control of their turf over to some hypothetical 'unity' government makes no sense at all.