Not only do we finally have confirmation that Mockingjay will be split into two films, but we also have release dates for both films! According to Deadline:
BREAKING …Lionsgate will release two films based on Mockingjay, the third book in Suzanne Collins’ Hunger Games trilogy. The Hunger Games: Mockingjay Part 1 will bow worldwide November 21, 2014, followed by The Hunger Games: Mockingjay Part 2 on November 20th, 2015. The first sequel, Catching Fire, is coming out November 22, 2013.
Looks like each movie will be a year apart (as opposed to the year-and-a-half wait between The Hunger Games and Catching Fire) and will be released around the prime Thanksgiving holiday box office.