Mireille Enos is hopeful that The Killing will return for a fourth season.
As for where the story could go in a potential continuation:
[EP] Veena [Sud] said — when they were breaking season three and they decided to have this ending — they talked immensely about the possibilities, but nothing is in place.
On her hopes for how Sarah Linden’s story is ultimately wrapped up if the series does go further:
I know that Veena loves this character. It would be so wonderful, after everything, to find Sarah ultimately in a place of peace, but I don’t know what that road looks like.