The sad part is, it isn't actually ever going anywhere. Probably. Ubisoft has said that there are no plans to ever bring Assassin's Creed's story into the modern age. And, considering how they've been pumping them out, it would very much surprise me if there were a long-term plan for the series at all. My impression is that it started with a cool idea, but now it's just in full-on money-milking mode. Which is a shame, because it is kind of a neat idea with a lot of potential if it were ever given proper focus and handled carefully.
In order for this series to actually go anywhere, and have any real meaning, Ubisoft actually has to take the step of admitting that it has an ultimate goal and end for the series. You can't just asspull a new maguffin and plot for each game as you go. Well, you can, but that usually turns a story into kind of a mess. But, doing that would also force Ubisoft to eventually retire one of its only popular franchises, and eventually, make something besides Assassin's Creed games.