The Return of the King? Mortensen approached for THE HOBBIT!
Even though Aragon is not in the original novel, del Toro & Jackson have approached the actor for a return to Middle-Earth.
Pre-production on The Hobbit is moving quickly now with the final planning nuts and bolts currently being worked out. According to Variety, it would seem that Fran Walsh and Phillppa Boyens will scribe the script for The Hobbit under the supervision of Peter Jackson and Guillermo del Toro. This was a partnership (minus Jackson of course) which worked extremely well on the Lord of the Rings trilogy. The bigger news though is that del Toro has approached Viggo Mortensen about reprising his role of Aragon, a character who is not mentioned at all in the original Hobbit book.
del Toro says..."We will all be involved in the script in some fashion but the exact definition is about a week away, " said del Toro. "I am all for keeping the actors who originated the parts, as much as availability and their willingness will allow."The trades also mention del Toro has approached both Ian McKellen and Andy Serkis to reprise their roles of Gandalf and Gollum respectively, two characters who play a big part in the novel. Actually I would go one further than that and say both actors have either signed or have shook hands on the deal with a verbal commitment to return. Both actors (who are involved greatly with their own website) had The Hobbit recently listed on their upcoming movie roles page. I would expect contact with Hugo Weaving (Elrond) soon as his character appears in the books and he has always spoke fondly of his time on the film. Outside of those four, I'm not really sure who else could return. The main character of the book is Bilbo Baggins, who was wonderfully played by Ian Holm in the original film but he's probably too old to be convincing enough to play a much younger version of himself now. Remember that live chat is going down on Saturday, where you will be able to put questions to del Toro and Jackson... we should know a lot more about their intentions after the weekend.