Maybe 12.0 or the battle for light expansion is a long way away, but we already have a speculation in development of bliz: new class Void mage.
I think the concept of each spell, its moves and the effect it does will make the battle theme of light and void stand out for this new playable class.
Man if only there was a spec that already deals with light and dark magic to do their job. It would take quite a disciplined mind to handle contradicting forces and use them in some weird alignment for the greater good.
This is speculation for the future, it is in development, we still don’t know how we are going to get to the battle of light and the void, this new playable class is just speculation.
Before we get any other class they’re gonna need to fix the current one, and then the next class to be added is bard.
Also possible they stop adding new classes, and move towards adding new specs to existing classes.
Other MMOs do it that way, and now that WoW has added a spec to an existing class there’s precedent here.
But the next void Mage class is in development, they are already working with the movements, effect, range of reach And other things
It’s neat. Perhaps it can be explored with the Void elves and Shadowmoon Orcs. 
Looks more like temporary powers like the ones we had in BFA.
This is not a leak either:
Subtlety Druid 
I said that this is not a leak because it is in development, that is, speculation has a lot of work to do, for example, how will the Lore of the void mage class be?
Class and spec identities are essentially a bunch of mass effect endings. What they should be doing is creating distinctive playstyles. Id hope if they go the route of creating 4th specs, theyll make an effort to define each spec. Not enhance shaman being blue bar fury warriors, or paladins being holy rogues, or similar.
With how screwed up blizzard has been for the last 3-4 years between brain drain, mismanagement, and Activision mettling, i doubt itll happen though.
Where does it say it’s in development? Your video starts with talking about void abilities made for the Sarkareth fight, says they “really seem to be” a new concept, then switches to talk about void lore for the remaining 90% of the video.
It does mention a “hint” from an effects artist but doesn’t look like it actually says what the person said.
I’m not saying it’s not possible. People were doubting the new evoker spec too, but we had datamined quests and lore for that. Do you have something more for this?
Im actually much more for this than a new class. Alot of the requested classes can easily be a spec of an existing one.
For example: bard could be a rogue spec and your combo points are music related similar to monster hunters hunting horn. (Your builders give different notes instead of combo points and your finishers are songs to buff).
Every fantasy is just about hit with the classes we have, so expand on specs. Makes sense to me. Moreso than trying to build a new one from the ground up without gutting other classes.
blizz balance team thinks they can take on a new class huh?
Or they could be maybe a priest who uses shadow and void based spells.
And yes I watched the video. There’s so many other classes that would be welcomed if they do add another one. I don’t think a void mage would be one of them though.
Maybe it’s another class that uses void magic.
New race: Void gnome.
I think it could possibly be a rework of Shadow Priest. That that is just a guess for me.
EDIT: Wait, nevermind. I was wrong.
Just play a Shadow Priest or an Affliction Warlock. There’s your “Void Mage”
Warlocks og void mages. Come at me! Yes, my face is a voidwalker. Thx for noticing.