One interesting point to make, is that in the new edition its been confirmed that the Legions of Nagash alliances can now take allies from both Flesheater Courts and Nighthuant, while before it was just Flesh Eater Courts. This is good since it means much of the new Nighthaunt stuff can be (and has been confirmed to be) usable as allies or even as part of the Legions of Nagash armies, but more importantly, it means the Mourngul can be used with Legions of Nagash, where before it was unable too. That model can have some potentially fun combos with the new Nighthaunt buffing units.
As for Blood Knight point drops, its been confirmed that they are going down by 20 points (enough to fit in the cogs endless spell amusingly, which gives +2 to all move and charge rolls, meaning that the warscroll that lets them deepstrike on a battlefield edge 9 inches away from the enemy turns that charge roll from a 9 inch one to a 7 inch one, much more manageable when you consider other buffs).
An also interesting note for a ghost themed army, is that a new artifact called the Ethereal Amulet makes a heroes save unmodifiable like Nighthaunt units, could be interesting on a spectral vampire, or in my armies case, Vampire Lord on Zombie Dragon conversion.