The sequel is in that chest. No, you cannot have it.

Capcom's Zack and Wiki: Quest for Barbaros' Treasure is a much-loved and highly regarded Wii title, having sat inside Metacritic's top 20 Wii games since its release nearly three years ago. Making the most of the Wii Remote, each puzzle required you to move it in a different way, but sadly the limitations of the Remote itself held back the controls from being completely successful. Now MotionPlus is out, could we see a more reliable sequel any time soon? Probably not, according to the game's producer.

Revogamers recently spoke to Capcom's Hironobu Takeshita about rumours of a MotionPlus-enabled follow-up, and the response was mixed:

Thank you for your love for Zack & Wiki: Quest for Barbaros’ Treasure! However, unfortunately that rumor is totally not true. I personally like this title so I would like to create a new one though I don’t think it’s good timing to do so.

Just like Tetsuya Nomura's desire to make a follow-up to DS RPG spectacular The World Ends With You, it seems Mr Takeshita may have to wait quite a while until he's able to produce a follow-up. Until then, you can wait patiently or berate anyone you know who didn't buy this Wii classic, which could take long enough to last you until the next Nintendo home console is released.

[source revogamers.net]