User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-77.189.255.113-20111218151133/@comment-173.61.121.132-20111219233922

Cha-Cha is still there. I believe you get Kayanba later, and can hunt with both of them. Except in multiplayer you have to pick one (or maybe the game picks one for you, I dunno).

Since everything's in Japanese, we don't really know about the story. I'd a ssume it's mostly the same as Tri, but possibly with some subplot about the new Elder Dragon.