The Wii U port of the 3DS title, Shantae and the Pirate's Curse, will release before the end of 2014.
In a tweet form developer WayForward, which you can see below, it is revealed the game will be available on December 25 at 9 A.M. P.T. for Wii U.
For our review of the 3DS version of Shantae and the Pirate's Curse, head here. WayForward's successfully Kickstarted follow-up, Shantae: Half-Genie Hero, is still in development.
[Source: @WayForward, via NeoGAF]
Our Take
Nintendo still hasn't made it an option, but I really wish in situations like this (or with another excellent WayForward title, Mighty Switch Force 2) buying one version of the game would unlock it on both Wii U and 3DS. It's a system that has been working well for Sony and PlayStation 4 and Vita.