I haven't read much of Diop's work. I've studied the archaeology of this region in depth though and therefore am very familiar with it.
I hope you read the beginning part of my post because I said that it all depends on how you define civilization. At what point do you say humans went from uncivilized to civilized? I see a major dilemma in that alone. To this day, archaeologists cannot agree upon what defines an empire from a state from territorial state and so forth. To tell you the truth, there is no easy definition because each civilization is unique and to identify cross cultural similarities that you can then say "this is what defines X" is practically impossible. For instance some scholars say having a written language is a necessity for a centralized state or empire, however the Inca Empire which was very succesful and larger than the Roman Empire did not have a system of writing. Therefore to say the Inca were not an empire due to not having this specification would be a grave mistake.
But the dates for the Akkadian empire are correct. Like I said, the earliest Egyptian pharoahs date back from 3000 B.C. which is before the Akkadian Empire. However, the political makeup of Egypt at that time (Old Kingdom) was very different from the New Kingdom time. The reason for the succesful unification of Upper and Lower Egypt is that there was strong cultural unity along the Nile and had been for some time.