But we already have Dark Apostate which is pretty similar to a death knight, and Pale Master Wizards could already be "death knights" beforehand.
I wouldn't mind a dark paladin tho, that's for sure, but let's just all classes get their archetypes first.
dark apostate is just a half baked pale master in my opinion, I don't like it and I think it's garbage. But that's just me, I never like playing clerics as is.
That aside, a death knight/black guard would have trapping skills, that in itself is a huge benefit since those skills are still class locked for some reason.
I wouldn't mind seeing archtypes for other classes, weapon master (though this is probably covered by Kensai ish?), or a dirge singer for bards, dragon disciples for sorcs and bards, shadow dancer for rogues, well. . . the list could go on, there's simply so much out there that can be used in this regard. So I imagine it will come when it comes.
Well there's the Undying Court & the Deathless in Eberron lore, so it's certainly a possibility especially if they start combining iconics & archetypes.
The feywild isn't actually going off fairy lore. . .or d&d lore so far as I can tell. I was pretty excited when I saw the expansion until I went there. . .but I'm pretty into mythology, especially about the seelie and unseelie courts. I was just hoping for more than what it was, so my fault on that front.
It would have been nice if they made it more dark and enchanting though, a place of foreboding and forbidden beauty that threatened to enthrall you and keep you there forever. . . but oh well.