Mission: Impossible (formerly Mission: Impossible IV) is currently in production.
Production Status
In June of 2009, it was announced that Tom Cruise would be returning as Ethan Hunt in the new movie and that both J.J. Abrams and Tom Cruise would serve as producers. It is not yet known whether Abrams will direct, as he did for Mission: Impossible III.
In August of 2009, it was announced that Josh Appelbaum and André Nemec would be writing the script, based off a story written by J.J. Abrams.
In May of 2010, it was announced that Brad Bird would be directing the movie.
In August of 2010, it was announced that Ving Rhames would be reprising his role as Luther Stickell, who was a main character in the three previous movies.
Also in August of 2010, it was announced that Jeremy Renner would be starring in the movie, alongside Tom Cruise. Reportedly, Paramount Pictures wanted to select an actor who could potentially carry on the series, should Cruise's Ethan Hunt character not continue to be the emphasis in future sequels.
In September of 2010, it was announced that Paula Patton would be in the movie, playing a young operative working with Ethan Hunt. Other actresses who were possibly up for the part were Lauren German and Kristen Kreuk. It was also confirmed that Simon Pegg would be reprising his role as Benji Dunn. And, apparently, the title for the new movie will simply be Mission: Impossible, instead of Mission: Impossible IV, as Paramount Pictures has chosen to "reboot" the franchise, although since many characters (played by the same actors) are returning, what they are actually doing is "revitalizing" the franchise, much like what they did in 2009 with the movie Star Trek.
Also in September of 2010, it was announced that Josh Holloway would be in the movie, playing a member of Ethan Hunt's team. It had also been announced that Vladimir Mashkov and Michael Nyqvist would be in the movie as well.
In October of 2010, it was announced that Léa Seydoux and Anil Kapoor will be in the movie, each playing a lead villain. The previously-announced Michael Nyqvist will also be playing a villain, alongside Léa Seydoux.
The release date for the film is December 16, 2011.
Rumors
Rumors at one point had arisen that Brad Pitt may become the star of the movie, although it was currently unknown at the time if Tom Cruise would or would not be chosen by Paramount (given their strenuous relations).