Assassin's Creed: "Hope you like Ezio" Edition.
Seriously, guys, another spinoff? You'd better be working on Number Three in the meantime, 'cause trotting out the same tired old horse over and over every year isn't going to cut it. There's only so much you can do with this guy, and this setting; you're going to run out of cool gadgets and interesting monuments eventually. Your gaming audience is ready to move on! Show us feudal Japan! Industrial England! Heck, even revolutionary America would be nice!
Also, we need some new characters. Ezio is nice, but he's also a bland everyman who happens to be an assassin. Give us a new, interesting character - perhaps one who actively strives against the role he's given? Or a martial character who has to learn to be stealthy? How about a female assassin? An African assassin (in Africa, even! The kingdom of Mali needs some attention.)
That said, I think I know one thing they're doing this time around: Multiple characters, multiple time periods. Ezio is following Altair's footsteps, right? What if you have segments where you (as the player and Desmond) can switch characters and time periods - traversing the same city from two different viewpoints? Solve puzzles (mostly involving finding clues in different time periods)? Assassinate extra characters? Run around various buildings-under-construction?
There IS potential here - but this is it. No more free rides. If you want our money, you need to earn it.