It's Official! Ian McKellen to Reprise Role As Gandalf!
"Yes, it's true. I spoke to Guillermo in the very room that Peter Jackson offered me the part, and he confirmed that I would be reprising the role. Obviously, it's not a part that you turn down; I loved playing Gandalf."
They also reported that Del Toro will be moving to New Zealand for the next 4 years in order to see the films through.