The next class in Diablo 4 will be the Warlock
As a result of analyzing the files of Diablo IV on the public test realm (PTR), enthusiasts have discovered possible confirmation of the addition of a second playable class in the Lord of Hatred expansion. This refers to the Warlock.
The initial findings included concept art hinting at a duality of light and darkness in the new classes but did not specify who would take the "dark" side.
New data posted by a dataminer on Reddit contains a file with the explicit name "2DUI_Expansion2_Info_Page_01_WarlockUpdate_0". This leaves almost no doubt about the class choice.
If the information is correct, Lord of Hatred will introduce the duo of Paladin and Warlock—an archetypal confrontation of holy faith and dark pacts.
Now, the main question is how exactly Blizzard will implement the Warlock's magic and how it will affect the gameplay and world exploration of Diablo IV.