Sega has announced that a stand-alone expansion for Total War: Shogun 2 is coming next year. It's called Fall of the Samurai, and it set in the time where Western technology and steam engines pushed the age of the samurai to a close. Old meets new. This should be great.
Sega says that this is a new, huge experience, featuring six new playable clans. Modern, imperial Japan will fight with the old Shogun, and they'll both have to deal with foreign powers. There are new abilities and units (39!), and ten new ships will be added in sea battle. Also expect new features, like naval bombardments and railways.
Look for Fall of the Samurai next year, March 2012. We've got a few new screenshots from the announcement in our gallery.