I think if Kislev were coming anytime close to launch they'd have announced it by now, but I definitely think they're still on the cards given the big deal they made about designing them with CA.
A Great War Against Chaos supplement seems inevitable, which is presumably when they'll cover Kislev and Chaos Daemons. I doubt FW will be able to resist the urge to release Magnus the Pious, Engra Deathsword and Asavar Kul models.