It seems that Raphael, Donatello, Michelangelo and Leonardo are running out of time. Like other digital content, it seems that the game isn't meant to live forever. According to Ubisoft, Teenage Mutant Ninja Turtles: Turtles in Time Reshelled is being pulled from the Xbox Live Marketplace and PlayStation Network on June 30th due to an "expiring license." This only appears to affect the US region.
This means you have less than one week to get your hands on a solid four player co-op beat em up starring your favorite 80's turtle characters. Bummer dude.
Source: Joystiq.com