Director Peter Jackson is in talks to extend the two-film series based on The Hobbit to a trilogy, according to Hollywood Reporter.  Additional shooting would be required, which would take about another two months in New Zealand next year, according to the report.  Rights and talent would have to be lined up to make the third film possible.

The material for expanding the films is in the "Appendices" to Return of the King, according to Deadline, which explain what Gandalf was doing during The Hobbit
Shooting wrapped earlier this month on the two-film series (see "'The Hobbit' Movies Wrap").  The Hobbit: An Unexpected Journey, the first film in the series, is scheduled to open December 14th.

--ICv2