Nintendo had a Classic Controller Pro on display at E3, but haven’t said anything official about releasing the accessory outside of Japan. Koei thinks we’re going to get it, though.
Their Samurai Warriors 3 fact sheet mentions the Classic Controller Pro twice. “Making its debut exclusively on Wii, Samurai Warriors 3 takes total advantage of Nintendo’s new Classic Controller Pro.” Then on their features list, “master the moves of samurai masters using the Classic Controller Pro.”
In Japan, there is a Samurai Warriors 3 bundle that includes a Classic Controller Pro. Maybe Koei plans on releasing it here when Samurai Warriors 3 comes out next year.