It appears that PJ is considering splitting the Second Movie to make a third; using the Appendices as reference material. It think it's a great idea, as it could tie together alot of the additional background history & characters that span The Hobbit & LoTR.
He may just 'add' material to create Extended Editions for the Blu-ray/DVD. But apparently he's thinking of shooting additional material in order to create a 'Third' film.
I hope he goes with the 'third movie' option