Sub-Saharan Africa has deeply rooted social problems, extreme poverty, frequent civil wars, rampant terrorism, political instability and large scale exploitation. Since the colonial era, most of the continent has remained in a state of anarchy or has been under the control of various failed states. Upliftment of the general population would require some form of stable democratic government.
I think African economic success, if it happens, will be through the effective use and regulation of their vast natural resources, not through the exploitation of cheap manufacturing and services industries as with Asia. This could lead to a unprecedented rate of growth in social and developmental indicators, especially median income. It's possible that this could happen in the later half of this century, especially with countries such as Nigeria.
Africa has a staggering amount of untapped manpower and resources along with a very young population, compare that to the aging and relatively utilized populations of developed and industrialized economies, and the already rapidly changing demographics of emerging economies and it seems the chances of the pendulum swinging their way is much higher. This would also lead to fairer global wealth distribution.