None of the Elves are mentioned by name, Legolas is from Mirkwood, his father is the Elvenking in the book so it stands to reason he would be there during the movie.
POSSIBLE SPOILERS
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As far as Old Bilbo and Frodo, I think I have read somewhere that they are going to start the movie with a flashforward to Frodo and Bilbo discussing Bilbo's book which leads to the beginning of the movie.
As far as Saruman, I believe Gandalf disappears right as they are entering Mirkwood as talk of the Necromancer comes up (which turns out to be Sauron). I would guess there will be a scene of the 5 wizards and the chief elves (The White Council) discussing what to do about Sauron. There are some theories that the entire White Council may go after the Necromancer/Sauron and do battle forcing him back to Mordor
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