Pajiba has gotten a hold of Christopher McQuarrie's script for X-Men Origins: Wolverine 2, and they have revealed the main characters in the movie. Beware, some spoilers are listed below, so read further at your own risk.
By request of Fox, this info has been taken down.
We also learn of a character named Shingen, whose late father was Master of the Hand. Shingen's father killed himself, refusing to let Shingen take over as Master with the hope that the Hand members would choose Logan as their new master. Kenuichio is the illegitimate son of Shingen who is also an adept Samurai warrior, although Shingen doesn't acknowledge Kenuichio as his son.
There also seems to be a bit of a love triangle here between Logan, Mariko, Shingen's daughter, and Yukio, Logan's bodyguard. There is also a corrupt Minister of Justice in Noburo Moro, who Shingen has arranged to marry Mariko, and even a character named Frank Sinatra, who provides Logan with information.
Of course, none of this has been confirmed at this time and we'll be sure to keep you posted with any further developments regarding X-Men Origins: Wolverine 2 as soon as more information comes in.