If Great Fall is actually legit, I think it may actually be the French Revolution. Jade Raymond said that the game is not set in Japan, and that it is her favorite time in history. Ubisoft is based in Canada which has a very big French influence. It could mean the fall of the Bastille.
It's not going to be Japan.
Even though this comes straight from the horse's mouth, I'm sure there will be some that say "Oh totally doesn't totally mean totally anything ,it totally will totally still totally be totally Ja-totally-pan... totally".
I think late 19th century Russia might be cool.