Tatsunko vs. Capcom: Ultimate All-Stars was published in 2008 when Capcom struck a deal with Tatsunoko Productions, a major animation production house in Japan. Only a small portion of their vast output has been exported to the America, with the best-known example being Gatchaman (called Battle of the Planets or G-Force here in the US). The resulting game was one of the wackier, and beloved, entries of Capcom's Vs. fighting series. One that is now officially out of print.
Siliconera was the first to report how, due to a licensing agree that lapsed fairly recently, Capcom is no longer allowed to sell the game, either in a physical or digital format. Which means any copies that remains on store shelves are the last ones you'll find.
Though given how long the game has been out, there's perhaps very few new copies available to begin with, unless one counts places such as eBay.
This heads up came from Christian Svensson, the Corporate Officer/Senior Vice-President of Capcom. When asked if there was a chance for a re-release for the Wii U, the reply was: "Unless Japan were to strike a new deal, I'd say the chances of this happening are slim."