https://www.techpowerup.com/309695/two-diablo-iv-expansions-in-development-at-blizzard
 
The Diablo franchise's general manager Rod Fergusson appeared on the Kinda Funny Xcast last week, only a few days before the fourth game's full launch - episode 140's interview segment focused on Blizzard's final preparations and post-game content (seasonal and possible DLC) calendar. Fergusson indicated that his team was very busy and will have more work to do: "As I sit here we're about to launch the main game, we're finishing up season one, we're working on season two, we're working on expansion one, we're kicking off expansion two…we're working on that now and we haven't even launched the game."

Blizzard Entertainment received much criticism for its slow and sparse trickle out of seasonal material for Diablo III, and Fergusson is keen to not repeat similar post-launch patterns with the latest entry in a very long running series (the first game debuted back in January 1997!). Diablo IV has been built with a live-service format in mind - thus allowing for greater and more substantial content to be delivered over seasonal time periods. Blizzard is likely aiming to compete with the likes of Bungie (Destiny 2) in terms of keeping an online game alive for a while - Fergusson outlines a key goal for his team: "We're going to be supporting Diablo 4 for years to come - (with) very rich seasons, much richer than we had in Diablo 3."
 
Hopefully the Diablo IV gaming experience will be improved. 
 

seems whack to announce DLC's only days after release.