UPDATE: Peter Jackson has officially confirmed the news, saying that the third film will allow him to tell the complete Hobbit story along with additional material from J.R.R. Tolkien’s Lord of the Rings appendices.
ORIGINAL STORY:

There’s some good news and some bad news for fans of The Hobbit. Director Peter Jackson is rumoured to be in talks with Warner Bros. to split the two-part Lord of the Rings prequel into three. That means you’ll get to spend more time in Middle-earth with more characters, locations, and sub-plots from Tolkien’s story, but the bad news is that you’ll have to wait an extra year to finish the journey.
The extra movie would require Jackson to shoot additional footage, which means that the actors and behind the scenes talent will need to get new and bigger pay checks.
The first movie, The Hobbit: An Unexpected Journey, will hobble into theatres on December 14. The second movie, The Hobbit: There and Back Again, will follow a year later. If the third film becomes a reality, expect it to follow in December 2014. There’s no word yet on a title, but our best guess would be The Hobbit: The Search for More Money.