Ian McKellen and Andy Serkis on for The Hobbit

Hoping not to lose anyone in the deal making process, Gandalf and Gollum both already agreed to do the next Hobbit movie. In an interview with theonering.net, director Guillermo Del Toro said "I had the most charming meeting with Sir Ian, and all bureaucracy pending, he’s on board, as is Andy Serkis. [...] It is our intention that we will not lose any of the key elements."

Considering Bilbo Baggins is the main character of the 'The Hobbit' book, Ian Holm might be getting the best deal out of the two movies. While the contracts for the first three 'Lord of the Rings' movies were probably signed before the movies got shot, the potential of the 'The Hobbit' movies is already known. It's like asking an extra figure for the payment of a sequel to a box office hit.

But the audience might not mind someone else playing Bilbo Baggins as much as someone else playing Gandalf. In a couple of months we'll know if someone was getting a little too greedy.