Egypt and Nubia

The 25th dynasty of Egypt was a Nubian one. Could the Nubians have re-conquered Egypt again? Perhaps between the Persian and Arab conquests, when Roman rule was weakening? I know of tribes settled south of Egypt such as the Blemmyes that did raid in Egypt, but I'm not sure how powerful they were.
 
Maybe the kingdom of Nobatia or Makuria later could seize the southern part of Egypt, but not the Nile Delta. Maybe if they managed to took the fortress of Babylon of Egypt...
 
Possibly, but if they did the conquering Nubians would most likely assimilate rapidly, becoming an Egyptian dynasty.
 
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