Diablo 4's first expansion is Vessel of Hatred and it's coming "late 2024"

eurogamer.net:

With this year's BlizzCon now firmly underway, Blizzard has been whipping up the crowds with a bunch of announcements during its Opening Ceremony, including initial details on Diablo 4's first expansion. It's called Vessel of Hatred and it's due «late» next year.

Vessel of Hatred — said to still be «super early» in development — continues the story of base game antagonist Prime Evil Mephisto, and introduces a new region to Diablo 4: the lush jungles of Torajan, last seen in Diablo 2.

Blizzard isn't saying much more about Vessel of Hatred just yet but it does tease that it'll feature «new ways to play», «new evils to vanquish», plus a new class never before see in the Diablo universe. There's also a (not especially informative) teaser trailer to accompany the news.

Of course, while official details might be limited right now, this isn't the first we've heard of Diablo 4's initial expansion; a number of details were datamined earlier this year and it's striking how closely they align with today's announcement.

At the time, leaks pointed to a continuation of Mephisto's story (under the title Lord of Hatred, but that's close enough in my book), as well as a returning region from Diablo 2. Dataminers explicitly referenced Kurast, which is, of course, a city not too far from the jungles of Torajan.

As such, it seems reasonable to assume leaks were on the money with some other features too, including word that the expansion's new class would be the nature-themed Spiritborn. Dataminers also unearthed references to a new Mercenary system — giving players the option to hire NPCs featuring their own levelling, skill tree, and gear slots — as well as to raids and the ability to craft corrupt Runestones.

Of course, none of that