It's not entirely impossible, though unlikely, that the Empire may conquer the Republic and then become 'Normanised'. For those who do not understand, after the Normans' conquered england they intermarried with the locals and were assimilated into the Anglo-Saxon culture.
So it is possible the Empire wins the war an loses the peace, so to speak. Basically Sith win, then through both their own infighting and jedi actions, are destroyed, Imperial citizens, join the Republic and a generation or two later they are fully assimilated into the Republic.
Thus explaining why the Empire has a Corusant accent, and that their raceism, which according to the OFFICIAL Atlas, was part of Core culture for millennium.