According to Not a Blog, one more of the two remaining major roles has been cast. He also noted that the Norwegian movie wolves that people have speculated would be the direwolves are not intended for those roles, because UK law makes it impossible. Our speculation is that the law doesn’t allow children and wild animals to work together. GRRM has also posted some cryptic hints to the persons identity.
The hints this time around are:
“Little Brother…
... was the great betrayer.
... worked at a tobacco factory.
... is a novel by Cory Doctorow that was nominated for the Hugo, but that doesn’t count.
... was the great betrayed.
... never went to space, but has been in freefall.”