Lots of info here:
https://www.diablofans.com/news/49145-diablo-community-group-q-aSome items I found interesting:
-Monetization. Despite the early development the team has pretty much settled on a base game supported by expansions as the business model for Diablo IV.
-The developers have lots of ideas for endgame systems and they want to offer a wide variety of things to do. We’ll get a preview of ‘Keyed Dungeons’ during tomorrow’s Systems & Features Panel.
-Sanctuary has hundreds of dungeons and you’ll be able to get ‘keys’ that unlock max level versions of those dungeons with special modifiers on them and better loot.
-Character customization has many avenues. In addition too items and runes there are skill and talent choices. While leveling or when ‘skill tomes’ you gain skill points that you can use to increase your skill ranks, unlocking new skills or empowering others. Skill point choices are permanent, but you will eventually be able to unlock and max all skill ranks. Talents are more playstyle choices and have effects on your skills, but will be respecable in the game.
-The developers are still early in developing trading systems, but the current philosophy is that crafting mats and consumables will always be tradeable. Powerful items will likely be bound on trade, meaning that can be traded, but only once. The most powerful items however will not be tradeable and likely stay bind on pickup. They want the primary source of items and power be from playing the game itself, so there are no current plans for auction houses, but there will be limited trading available through clan banks.
-Clans will be in the game and they will include clan banks to help with trading, but no other details were given.
-Loot drops will be individual to the character like Diablo III currently is, but if you drop an item on the ground, everyone will be able to see it.
-There will be a Hardcode mode
-Diablo IV is being designed as a massive immersive world with partying and group in mind, so there are no plans for an offline only mode, but there will be options for those who only want to play solo or only play with friends.
That last one is important- a lot of this stuff looks cool but makes me nervous, ultimately I don't want Diablo to be WoW.