Assassin's Creed 3 came out in 2012 and that was the one where you finally save the world. All that Mayan prophecy NWO conspiracy stuff finished with the Desmond games and after that they just tried the formula in new settings but honestly the story isn't so interesting anymore when all you do is parkour around olde cities and keep doing relatively small battles against the templars over and over and over again.
There's no mystery left and no new cool shit to do even in terms of gameplay. I guess that's what happens when you release seven games in seven years. They need to do something radical like have you battle against Juno 30 years in the future and have the "ancestor" memories be modern day events. And not release a new game every damn year.
But yea that's ubi.
Like Sunblade said, you don't really save the world in AC3 (which pissed me off, but that's for another time.

). They're continuing the Meta-plot with Juno plotting things in AC4/Black Flag. I haven't gotten around to Rogue or Liberty yet since I'm waiting for those to hit $30 or less on Steam.
It's why I'm not hyped for this new one either. Ubisoft hasn't discounted the others in the series on PC to a $10-20 price-point for me to blow through for the meta-plot or setting anymore.