Hmm, I wouldn't call them main characters, apart from Thorin. Most of them get barely a word in. I think the number is seen as magical, especially as Bilbo is chosen as member number 14, so we don't get the unlucky number 13.
Obviously it was always going to be The Hobbit, as it's about the normal man (or Hobbit) learning about the world and pushing down boundaries.
I wonder if all of their names will be mentioned. Obviously they WILL all be named, but I wonder if they'll be referred to on screen. I hope they also don't have brightly coloured hoods, as that falls into the 'childlike' element of the story that Tolkien later admitted wasn't in tune with LOTR, writing off the tone of the Hobbit as Bilbo's child-like memoirs, which obviously became the Red Book, which is where I hope the film starts, with Ian Holm back as Bilbo beginning to write the book as in FOTR. Then we can have him write and say the line: "In a hole in the ground there lived a Hobbit" Then we go to maybe a different actor as the story begins. That way Ian gets a good role that all the fans will be happy about, plus we get the famous line from the book to kick off the 5 films, and by the end of the films we end with that other famous line "Well, I'm back."