In the midst of all the backlash that was received during Blizzcon 2018 forDiablo Immortallast weekend, Blizzard apparently were going to announce more than just Diablo Immortal. According to sources close to Kotaku, a video was pre-recorded revealing the Diablo 4 title.
Rumour: Diablo 4 Was Going to Be Announced At Blizzcon 2018
A twist has been added to mix of last week’s events, a pre-recorded video has said to have been prepared for an unveiling of Diablo 4 originally atBlizzcon 2018, but later was pulled from the event. It was set to feature Blizzard co-founder Allen Adham releasing that Diablo 4 was being developed.
However, since thisinformation was released by Kotaku, Blizzard have commented that the video they mentioned was not meant for BlizzCon.

First off we want to mention that we definitely hear our community. We generally don’t comment on rumors or speculation, but we can say that we didn’t pull any announcements from BlizzCon this year or have plans for other announcements. We do continue to have different teams working on multiple unannounced Diablo projects, and we look forward to announcing when the time is right.
While Kotaku’s sources have said that a video was made, means that Diablo 4 is indeed in progress. According to the article the title has undergone a couple of “different iterations”. How far they have gotten with this game is also in question.

In a previous blog post by Blizzard also said something similar, they did mention that “multiple teams working on different Diablo projects…” but never mentioned any particular names.
Diablo 3 still remains the most recent title available on PS4, Xbox One, PC and recently launching on the Nintendo Switch. The announcement ofDiablo Immortal coming to mobilewas also made with no announced release date as of yet.