A guy on reddit who has been spot on with leaks in the past had the following to say about Diablo 4.
Diablo 4 is actually going to look dark, gritty and gross - no more rainbow shiny bullshit this time! Loactions are toned down, infrequently laid with corpses, wasteland, greyish deserts, clut caves surrounded by flesh, rotten crypts, marshes and bogs, plagued cities you name it. They are also seemingly much bigger, maybe even open? Characters now are able to ride horses (possibly other mounts), also there's contextual interaction with environment ? - climbing a wall Lost Ark style. Blood splatters look more like blood and not splashed jam too.
So far i can confirm 3 classes: mage (uses fire, ice and lightning so far), barbarian (swords, clubs, axes, kicks etc), and druid (lightning, wind, and transforming into beasts - so far bear and werewolf!).
Possibly there will be PvP from the start?. 4 player coop is there for sure.
All this game seems to be is a W I N K to the Diablo 2 fans, Lilith being the new diablo (she's covered in blood veil kinda), characters being shown sitting at a campfire as character selection, nitty gritty dark style that 2 was praised for, some skills also seem to be just taken from it and put in here (like sorceress' charged bolt). I'm interested and hope they don't fuck this up. The company is bad, but the game might not be this time.
2 points with "?" are just because it's not clear to me tbh... let's see what they say at the conference
no date yet too.. sorry.. If any questions I will answer later
I don't like the sound of larger areas as I think loot games feel much better to play when they are in compact areas, that way you are not having to uncover a massive map in fear of missing out on some loot. I wasn't that bothered about the look of Diablo 3 so the move back to a darker world is whatever.