I just read over on ComicBookMovie.com that James McAvoy has an interest in playing Gandalf in "The Silmarillion" which is the prequel to The Hobbit and Lord of the Rings saga. Below I quote from CBM.com
“I’d like to play Gandalf,” said McAvoy, laughing. “It’s called The Silmarillion! It’s a collection of poems and songs that chart the ancient history of Middle-earth. My true geek is coming to the fore, but they’re really, really beautiful stories. In part of that is the genesis of Gandalf, or Mithrandir, or Stormcrow, or any of his many, many names. Anyway, maybe that’s the one!”
While a "The Silmarillion" movie would be a beautiful thing to behold I fear the chances of it getting made are rather small because it would require a very big budget but that's just my opinion and I could be wrong. I remember reading over on Jackson's Facebook page that the third film in Peter Jackson's The Hobbit trilogy will be a prequel within a prequel in that it's actually based off of The Silmarillion.
Nonetheless, I think that The Silmarillion would do far better as an anime TV series because the book is very episodic in it's structure and story. I really loved Cartoon Network's ThunderCats 2011 reboot and I think that a studio like Studio 4°C or AIC ASTA/Aniplex would be the absolute perfect choice to create a Silmarillion anime TV series.