Well, from what I hear they're also going to use information from the Appendices of LotR that adds backstory to the events of The Hobbit. They're also going to include what Gandalf's actually doing when he leaves Bilbo and the dwarves. But ya, I still don't think there's enough content, which is why I'm almost resigned to the fact that PJ is gonna make junk up.
"Suddenly Frodo noticed that a strange-looking weather-beaten man, sitting in the shadows near the wall, was also listening intently to the hobbit-talk. He had a tall tankard in front of him, and was smoking a long-stemmed pipe curiously carved. His legs were stretched out before him, showing high boots of supple leather that fitted him well, but had seen much wear and were now caked with mud. A travel-stained cloak of heavy dark-green cloth was drawn close about him, and in spite of the heat of the room he wore a hood that overshadowed his face; but the gleam of his eyes could be seen as he watched the hobbits."