Apologies if this has appeared in another thread, but it's pretty recent.
"The Hobbit Stars Ready For Action"
http://www.bbc.co.uk/news/entertainment-arts-12434929
If this dull American isn't mistaken, Bilbo is being happily played by the charming young porn star from "Love Actually," who did manage to make time despite filming Sherlock.
(I can't find the BBC article that mentions David Tennant allegedly playing Thranduil.)