A Hardcore server type has appeared in the game’s database table in Patch 10.0.7, which means we could get official support for Hardcore Classic realms soon.

How Would Hardcore Realms Work in WoW?

Similar to Diablo, when your character dies, it will get deleted. Classic players currently replicate this behavior by using an addon, but some datamined strings hint at possible official support for Hardcore Classic realms. Specifically, the cfg_categories database table had a Hardcore string added in Patch 10.0.7 Build 48295.

Now, all we need is an official announcement by Blizzard.