This would never happen for 2 reasons
1. 60-70 % of all natural resources that feed the world especially europe comes from africa. If they nuke the continent they remove all the precious minerals oils and steels etc that so many on the planet need including themselves and they are now left surviving from unnatural and modified food which they know will ultimately kill them. Not only that but the gadgets and electronics we use today many of the main chips and uranium zinc etc used to manufacture these phones flat screen TVs etc come from the african continent. Destroying that continent puts the world back in the stone age. You would not just be killing the people you would be killing the animals, vegetation, all the pure minerals. Killing us they would be killing themselves.
2. White people understand their own nature and have understood it for a long time. They know how combative their nature is and how they spent centuries at war with each other. Removing all black african people will only lead to them then going after all Asians next, then east indians, then ultimately they will once again be at war with themselves again. US being their open enemy keeps them motivated in unity to always advance to maintain their power. Remove us and it will have a ripple effect on their power structure.
They can atrempt, as they have been doing to make it a biological war but the problem is its not enough of the world that hate us yet to pull off annihilating us without getting a over flow of support and ultimately you could turn a poor nation to a very rich nation just on financial donations if it becomes too known that they are out to eliminate us. So the slow and gradual process has been taking place for hundreds of years.
It's not pan african thought that will eliminate us, our unity is what pushes their agenda backwards. But right now enough africans on the continent hate us in america, enough of us here hate those in africa, enough of those in the islands don't like those in africa or america, and so forth so that hatred and disunity is then manipulated to their advantage to continue the slow and quiet strategy of killing us a little at a time. What we must look out for is when the world hates the "nikkas" enough where they won't care if we are all gone as they see us as a waste of space. Then we need to worry. Especially if they can convince the world that us getting "ebola" or "aids" is somehow gods will and it's in God's will for us to be eliminated , because we didn't follow his "laws statutes and commandments" etc.