According to PSM3 Magazine, Assassin’s Creed 3 is rumored to take place in Egypt. The news has not been confirmed by Ubisoft. The series does take place in major cities throughout history. Jerusalem, Rome, Florence and Constantinople were major destinations that brought together all sorts of people and religions from around the world. Egypt can easily fit in.
–Warning: Assassin’s Creed: Revelations Spoilers–
It makes sense for the series to go to Egypt given the direction Assassins’ Creed Revelations has taken. Altair’s son, Darim, wrote that he moved his father’s books to the Egyptian capital of Alexandria where he is staying. Since AC: Revelations is the last Altair, Ezio game, Darim, would most likely be the next lead character.