The story is described as 'an epic' and nobody really knows at this point how long it will go. I suppose Ubi will keep finding amusing, beautiful, interesting, and obscure pockets of history for us as time goes on. Maybe that's why they started 900 years ago, to leave so much time for Desmond's ansestors. You can fit a lot of them into that time... I once researched Robert de Sable's desendants... Four hours. FOUR HOURS. He was related to Winston Churchill, Princess Diana, and Anne Bolyen, though, which is cool.
Where to go? America, sooner or later. It would be really interesting to go to the days settlers first arrived, where the main enemy was the natives. It could provide some intellectual material, too, seeing as an assassin and the templars would be on the same side against the natives, but still fighting amongst themselves... It's kind of hard to explain, forgive me ^^;