Not a whole lot of details from this particular announcement, but Collider spoke to Fox CEO Tom Rothman at Cinemcacon, where Rothman reportedly "all but confirmed that a New Mutants movie will be announced soon"---
Collider:When can fans expect an announcement on some of these other properties? Before Comic-Con, after Comic-Con, at Comic-Con?
Rothman: In the summer.
Collider: Are you talking to filmmakers right now?
Rothman: Let me just say this. All I have to say is, I agree with you in your assessment of the potential in a lot of these [Marvel] characters.
X-Men: First Class definitely changed the vast majority of opinions here about Fox and their handling of the X-Men franchise. Of course, many attribute that turn around to Matthew Vaughn and the film's talented acting ensemble so it will be difficult to formulate an opinion about the project until more details are revealed.
The New Mutants are a group of teenaged mutant superheroes-in-training published by Marvel Comics. They have been the main characters of three successive comic book series, which were spin-offs of the popular X-Men franchise.
The first team of New Mutants characters was created by Chris Claremont (long-time writer of Uncanny X-Men) and artist Bob McLeod; although the concept for a "X-Men-in-training team" was originated by Uncanny X-Men artist John Byrne in a letter he wrote to Claremont in 1978. They first appeared in 1982's Marvel Graphic Novel #4 and were subsequently featured in their own title from 1983 until 1991. Also, like its parent title, The New Mutants highlighted interpersonal and group conflict as well as action and adventure, and featured a large ensemble cast. With the end of the first series, the characters were relaunched as X-Force in a new, eponymous series.
The second New Mutants series, launched in 2003, featured a new group of teenage mutants; but unlike the original New Mutants, they were only part of a huge cast of students at the Xavier Institute. At first, they were notable for their drive to become superheroes, but soon rival internal groups played a large role in the series. In 2004, it was relaunched as New X-Men: Academy X, after which the central group was formally dubbed the "New Mutants." In the aftermath of the "M-Day" crossover storyline in late 2005, the remaining students were merged into one junior team, the New X-Men.
The third New Mutants series, reuniting most of the original team, launched in May 2009.