Hugo Weaving, Andy Serkis and Ian McKellan are Hobbiting! Guillermo del Toro has confirmed that all three will be back as Elrond, Gollum and big ol' gray-hat himself, Gandalf in the new THE HOBBIT movies, set to start shooting next year. 

The films are to follow the plot of THE HOBBIT, with "extra" material from other work Tolkein works thrown in to round out and lengthen the story. 

Still to be decided? Who'll play Bilbo, the main hero of the tale.  There's some talk of James McAvoy for the role, which would suit me just fine.  I've been a major fan of his since CHILDREN OF DUNE. He did a nice job playing Mr. Tummus in the first NARNIA film and was pretty decent in WANTED as well.  So having him put on the hobbit feet and trounce across New Zealand wouldn't be a bad thing at all.

Source: The Hobbit: Weaving, Serkis and McKellen confirmed - Den of Geek