Assasins ending (spoilers)

I didn't understand the ending for assasins creed, I thougt it was left open for the sequal but now I find out that there is goin to be a new hero instead of altahir. So am I missing something? Cause I remember the game ending when I went into the room and den all these writings came up and done. i'm lost , so can someone fill me up I already sold that game so I don't want to play it again for a different ending. So yeah someone want to tell me what exactly happens?