Well, here's a weird story. MTV spoke to Dominic Monaghan, former Hobbit in The Lord of the Rings, and he says that he and the other original quartet of Fellowship hobbits might be back for, well, The Hobbit.
Now without extensive rewriting, Merry (Monaghan), Pippin (Billy Boyd), Frodo (Elijah Wood) and Sam (Sean Astin) do not at any point appear in The Hobbit - so we're guessing that, if they are indeed back, it'll be in the mooted second film, the bridge between the original story, wherein Bilbo travels with 13 dwarves to slay a dragon and steal its treasure, and the events of The Lord of the Rings. Given that Frodo, the eldest of the quartet, isn't born until some 27 years after the events of The Hobbit, even that interpretation involves some considerable narrative wriggling.
The story doesn't give any specifics, but you can read everything Monaghan has to say here, and let us know what you think below.