Obviously two films are being made. One will deal strictly with Hobbit shit - including some stuff that's mentioned but never documented, like Gandalf vs The Necromancer. The second is going to be separate from The Hobbit and apparently more LOTR flavored - a direct prequel.
The Hobbit novel is a "prequel" to LOTR in the simplest definition of the word, but obviously the books are very different. The Hobbit is a children's book full of happy times whereas LOTR is more bleak and complex. That's not a criticism of The Hobbit, I love the book, it's just different. Notice how GAY (happy) the elves are in the Hobbit compared to the brooding, somber elves in LOTR for instance