Game Informer released two Diablo 4 gameplay videos with BlizzCon 2019. One of them is about the barbarian, the other about the sorceress.
The content of both videos is approximately the same and designed to show how different the gameplay for each class. During the video, both characters left the starting location and went to the dungeon to kill the boss.
Diablo 4 has a lot of differences from the previous part: in addition to the changed visual style, the developers made an open world, added riding pets and other mechanics. All the details of the new game can be read in one big article that coming soon.