User blog comment:D. Cello/Assassinews 03/01 -- Assassin's Creed III era and boxart revealed/@comment-1192086-20120302023726/@comment-178.167.149.122-20120302024603

It's been in development for 3 years. I can guarantee you that a 3 year schedule (not forgetting another 8 months til release date) means it will be made from scratch. I wouldn't be surprised to see a new engine and completely new mechanics.