Here are some clues to what might happen in AC3.
1. At the last multiplayer video Warren Vidic finds the location of William Miles and tells the recruit to go get him.
( This might mean the Assassin team is being tracked by the Templar Agents or Abstergo Agents )
2. At the end of Revelations Desmond is at the Central Vault/ Grand Temple.
( This might mean the Grand temple has the thing that will stop another Catastrophe or help Desmond become the Ultimate Assassin )
3. Altair's Son takes some of his books to Alexandria.
( This might mean the team travels to Alexandria to find the books )
4. At the end of Revelations ( If you payed attention closely ) you can see a lady in the background simmilar to Eve.
( This might be one of Desmond's targets or another Contact. Maybe eve's decendant )
Now I have a question: Doesn't Desmond have to kill Eve's Decendant since he is Adam's Decendant?