Because the film had a relatively small budget - when I say small I mean around $34 million- and the fact that the film made just over $90 million at the box-office - it has now been said that a second adventure is "70% sure" of happening.
Mirage Studios Steve Murphy told The 5th Turtle: "As of two weeks ago Imagi Entertainment (the TMNT movie animation studio) informed Mirage Studios that there was a 50-50 chance of a CGI film sequel. Last week they upped the odds to 70-30 in favor of a sequel, as talks between Imagi and their distribution partners Warner Brothers and the Weinstein Group seem to be heading in a positive direction."