Ditto to Admiral Raven. I have no idea when it will be coming out, but DANG it looks amazing. The castle sieges in particular blow my mind. Trying to attack a castle build on top of sheer cliffs with only a few narrow approaches to bash away at the wall only to find another ring of walls behind it. Just insanely cool. It doesn't sound as formulaic as Rome Total War was (while being an amazing game, sieges tended to be very similar).
I saw a 4 page preview in PC Gamer that absolutely blew me away. I'm salivating over that game.
(Medieval Total War 2 - Winter 2006)