Obviously, this will involve new filming, new scripting, new everything. There's much speculation about where he cd break Bilbo's story into three pieces, but I don't think that's what they'll do. Consider: it's only four and a half months until the release date of the first film. Given all the special effects, scoring, editing, &c. they'll have to do, it's too late to change that one much. Besides which it's clear from hints Jackson has been dropping for a while that he really wants to film material from the Appendices (which for all events and purposes means Appendix B, supplemented by Appendix A). So I think the two HOBBIT films will remain pretty much as they are, and that the third film will be a 'bridge' spanning events from the years between Bilbo's return home and the Long-Expected party sixty years later. We know a lot about the events in these years, but since Tolkien chose not to write that story, any movie based on these materials will obviously contain less Tolkien, and more Jackson, than any of the other five. We'll see what they come up with.
Four and a half months to go . . .
current reading: WHERE THEY STAND and MEMOIRS OF HECATE COUNTY