I think it might be the final 2 Desmond sequences, i.e. to sets of pillars you can't enter, plus something more with Desmond out and about. "Part of the Creed (10) Take the induction leap of faith" makes it sound like Desmond might actually become a full Assassin with his Dad there.
Depressingly however, if these are real they only add up to 250 making the game 1490 total.
Last edited by Man Demon; 02-14-2012 at 12:46 PM.