I've actually considered the American Revolution/Revolutionary War myself, or perhaps rather the (global) events leading up to that period in time. I'm thinking ca. 1750 and onwards being the next logical "leap forward in time" for the AC series. It could include the French and Indian War/Seven Years' War. Should be loads of good stuff the AC writers could use there, especially considering the presence of Freemasonry and the like at that time.
Yup, could make a pretty good story right there, fighting Templar among the Redcoats, French and native Americans.
EDIT: Hehe, just realised the date on this thread. Ah well, no matter...