There is some datamined yet encrypted content regarding current Lich King and potential Death Knights form every race (even those post WotLK ones).
Perhaps it’s some small thing that will give us made up explanation why there are now even more new Death Knights of the new races BUT what if main story focus after whole deal with Nzoth will take us back to Northrend or at least will include Lich King?
We know Sylvanas is still plotting something and that she wants a way to stall/stop her inevitable death. So far she wanted to use Forsaken as her meat shield and personal army. Yet those efforts failed, so where else can she get huge, loyal undead army and power to rise Val’kyrs? Lich King’s “crown”!
What if that’s her goal? She knows of Bolovar (if that short story of hers wasn’t retconned) and perhaps want to use her new gained undeath powers to dethrone him and finally become Lich Queen that ppl were accusing her of being since Cata?
I have mixed feelings about this.
I loved WoTLK, and is probably my favourite expansion (followed by Legion don’t @ me). And I loved the wholed Death Knights and Frozen wastes and all the spooky shenanigans … back in WotLK. Now do I want to get back to it? The story lover in me says “no” because, we’ve been through it and it seems like they would be rehashing the story if that were the case. However, the player in me that has lost faith in good story writing is like “yeah sure why not”.
New races DKs would be kind of odd since, those races weren’t introduced in WoW back then and I am not sure if Alliance and Horde were cool with Bolvar raising new Death Knights, I mean he is supposed to keep the dead in check, not make more. But then again it would make sense to some extent to use the “Scourge” to fight the Void however SPOILERS* apparently that gets taken care of in 8.3 SPOILERS so I don’t know.
And who knows what the goal of Sylvanas is, I feel like it keeps changing. But becoming what she swore to destroy is a bit clichee for her I think. Would be too generic.
bolvar has been raising new death knights for a while now his totally cool with creating more he was pretty shady in legion
Oh has he? Bad Bolvar BAAAAD!
In the legion mount quest for death knight he even tells that if you fall here he will retake the ebon blade as he has plans for them
Sigh, just a minor setback then.
Nah good bolvar!.
Death to the living and glory to lich king!
(For now atleast )
Well sadly cliche story and reuse of ideas from the past are trademarks of Blizzard story writing. If MoP2.0 we just had is not enough than lets take a look how they copied ideas from Diablo, Starcratf and Warcraft to each other so many times that stories in all their games blur together. 
We were doing so throughout the entirety of Legion and no one had an complaints.
Except the paladins, but that was more because we sent a battalion of ghouls to ransack light’s hope first.
If we speculate even further, and add Ogmot’s Dream Journal quote in here, paired with the datamined things, an expansion featuring the Lich King can be very likely.
Ogmot writes:
''Three lies. Da first one been told.Bound by dat throne? No. Free. Free!"
I believe this is referring to the Lich King, seeing as he is bound in ice, physically, but also in the way that he needs to return to the Frozen Throne as we have seen, and does not stray far from it. I think this might be a lie now, or at least something has changed.
I’ve totally forgot about that journal and indeed it does “click” well with datamined content.
There’s a lot of stuff in there people seem to have forgotten. It’s full of small treasures. It even seems to hint at everything that has happened so far, with Sylvanas and the Horde, and a lot of other stuff.
Yes many major thinks of BfA was there. Still don’t know who was awakened Azeroth? Old god? And the path, from where to where?
I’d love to see a Wrath 2.0 take place after the disaster that was BFA. In fact, I’m almost convinced that it’s exactly what they’re building towards.
there must always a be lich king and the dk player is stuck sitting on the frozen throne for several expansions unable to do anything but watch
Well if they made it like Garrison/Order Hall where I would be able to send my undead underlings on missions and watch them level up and gear up I’m fine with my DK being AFK for couple expansions. Specially if they would bring enough gold from those missions that I could pay for few months of game time in advance! Beats farming herbs in Nazjatar.
but you wont be able to mail that money to your main though as you’d be frozen 
I seriously doubt it. Worst case scenario we will work with Bolvar to stop Sylvanas and her master, whoever he/she is.
don’t worry uruk when your popsicle i’ll still come to visit
Sounds good. I’ll make you a permanent resident of my little clubhouse.