http://shoguntotalwar.yuku.com/reply/924857/New-Factions#reply-924857
At E3 a SEGA Europe employee confirmed that there will be 8 factions in the campaign and one for the tutorial. People should disregard the so called ninth faciton, unless they announce something that confirms it. There are still a lot of things that can change. Its only in pre pre alpha.
9 factions pour la campagne principale plus 1 pour le didacticiel.