Capcom's rights to the Tatsunoko license lapsed "fairly recently" according to Capcom's senior vice president Christian Svensson, which means the company is no longer allowed to sell the title digitally or physically.
Posting in the official Capcom forums in response to a user question about whether the Wii version of the game is backwards compatible with the Wii U, a Capcom community moderator said those who already own a copy of the game on Wii will be able to play it on Wii U.
Svensson added that due to Capcom's rights with Tatsunoko lapsing recently, unless the company were to strike a new deal, the chances of Capcom being able to sell any Tatsunoko game "are slim." Once stores run out of existing stock, without the renewal of the Tatsunoko rights, they will not be restocking the game, nor will it be made available digitally.
Capcom struck a deal with Japanese animation house Tatsunoko Production in 2008 to published the cross-over fighting game Tatsunoko vs. Capcom: Ultimate All-Stars. The game features characters from both the Capcom and Tatsunoko universe.