At this point I think Bjork, deadmau5, Kendrick, and someone who doesn't really deserve to be a headliner but is going to be anyway, sound like reasonable guesses to me. It seems possible that My Morning Jacket will be back, but I'm just not sure I see them headlining again.
I was researching some of the other lineups and I don't know who Joywave are but they are playing Vancouver in March and then skipping the rest of the NW after that. They played in Seattle in October but they also played Vancouver then too.
They do this song, which I quite like:
and are featured in this song, who I also expect will be on the lineup: