Update: David Vonderhaar has now clarified that he was only referring to Blackout (the battle royale mode). Hardcore modes are expected to be in regular multiplayer.
Treyarch studio design director David Vonderhaar has discussed hardcore modes in Black Ops 4 for the first time answering a fans query on Twitter.
Hardcore is a variation of the standard playlists in Call of Duty, which has been a feature in every CoD multiplayer so far, and has had its own dedicated community for years.
It strips the game down to its barebones, removing the HUD, ammo counts, and leaving only the player and their weapon. Health is also set to 30%, meaning players die in 1-2 bullets typically.
Another notable point, is that in previous games, there was no health regeneration in hardcore, which is where the problem perhaps lies for Black Ops 4.
There is no more automatic health regen in Black Ops 4, instead players must manually heal, but this leaves a problem for hardcore - would manual healing just be removed entirely?
For now, it seems that Treyarch have not come up with a solution for hardcore, as Vonderhaar responded to a question asking "is the hardcore mode in Black Ops 4? and is it still no health regeneration", answering "not yet."
— Lord Vonderhaar (@DavidVonderhaar) September 29, 2018
This response likely means that hardcore is not going to be available at launch, which will be a major disappointment to a large portion of the Call of Duty player base.
While the standard 'core' playlists have always been more popular, hardcore has been a warranted playlist in all previous games, with many players much preferring it to the bullet sponging in core.
Vonderhaar's answer certainly leaves room for optimism that it could be added in the future, but it will not quench the desire of a lot of players.