[Update #2]: World of Warcraft: Cataclysm will be getting the Classic treatment and many new improvements in 2024.
[Update]: World of Warcraft: Classic has now launched Hardcore servers, and I'm happy to say they're quite fun!
After witnessing how popular the 'no death' runs have been in World of Warcraft: Classic over the past couple of months, Blizzard has now decided to make the whole thing official. As such, on August 24th WoW Classic will be getting Hardcore realms with slightly adjusted rules and only a single shot at life. This means no resurrections, reincarnations, soulstones or anything similar.
If you end up making a mistake and kicking the bucket, don't worry as you character won't simply disappear. By using the Free Character Move service you'll be able to transfer your character to any Classic Era realm, though obviously Hardcore servers will forever be locked for them.
PvP will also work differently. In order to fight enemy players you'll both need to actively flag yourself for PvP by typing in /pvp, so there won't be any sort of ganking or griefing. PvP Battlegrounds, on the other hand, are going to be completely disabled as they would simply not function with permadeath enabled.
In terms of endgame content, everything will be available from the very start, though don't expect to see many people going into raids given how easy it is to make a mistake and lose your character in there. On the other hand, lower level dungeons will have a 24-hour lockout timer on Hardcore realms to prevent overly safe play and force people to actually head out into the world and help each other out.
The final thing worth mentioning is that Blizzard will be taking a harsh stance against any sort of griefing. Trying to get other players killed by pulling elite enemies into them, deliberately causing wipes in dungeons or raids, and other such unwanted acts will result in major punishments, including account closure.
On the flip side, abusing this system and attempting to falsely report other players will incur similar punishments as Blizzard wants these realms to be taken seriously. A noble idea, but I can't imagine it's going to be an easy one to police given how little difference there is between intentionally griefing and just being terrible at the game.
Whatever the case may be, I'll make sure to let you know once the Hardcore realms go live on August 24th. Until then, you can read a little bit more about them over at the official website.