Assassin's Creed wasn't marketed as a two-parter/trilogy or whatever it becomes and I don't believe it was known to be this way prior to actually playing it. Yeah you did eventually beat the bad guy, but that was hardly the REAL focus of the story. By the time I finished the game I couldn't care less about Altair's enemies, just the overarching story of the templars/assassins.
I don't think AC gave a TBC message either, it just ended with mass assumption.
