Most Daughters of Khaine are dynamic and thematically strong enough to fit the new aesthetic, and are one of more complete "holdover" factions in terms of their range. I think they'll eventually get repackaged on rounds with a battletome, but might not get a new miniature release.
Darkling Coverns models currently look very intentionally static and regimented, and I suspect the whole faction will eventually be replaced or dropped.
Scourge Privateers obviously have a very strong theme, but nautical armies (i.e. sea monsters, etc) are quite difficult to model in a land-based game with terrain bases. However, I heard a rumour that the Fleetmaster is in WQ now, so they might get a repack.
Shadowblades are a cool concept, but a whole army of assassin-type models seems unnatural as they are an archetype that obviously relies on stealth. I think these two units, especially Dark Riders, are the most likely to get folded into the Shadowkin.
Order Draconis are a strange concept to base a army around, and I don't think they will survive as a long-term faction.
Either way, I think the Shadowkin will basically be a entirely new faction.