Diablo IV has been hotly anticipated, though last year's disastrous Diablo Immortal reveal, as well as the controversies surrounding Blizzard due to their handling of their banning of Hearthstone Pro blitzchung after his pro-Hong Kong statements might have doused that anticipation a smidge. However, with Blizzcon coming up the first weekend in November, one of Blizzard's announcements may have been leaked early.
Per the German site, GameStar, the recently distributed German magazine has an ad insert which talks about an upcoming Diablo art book, slated to release one day after Blizzcon 2019. The ad references Diablo IV, stating when translated, "over 500 artworks from Diablo, Diablo 2, Diablo 3 and Diablo 4," according to Polygon.
BlizzCon 2019 new Diablo 4 leaks in Germany. If this is true, information about previously leaked Overwatch 2 may be correct. pic.twitter.com/J3cmfciGNt— Naeri x ??? (@OverwatchNaeri) October 20, 2019
When translating the GameStar article via Google Translate, the magazine claims that the ad wasn't directly from Blizzard, rather it came from the art book's published, Panini. They do mention that one Blizzard's in-house senior writers, Robert Brooks, is listed as one of the two authors.
This wouldn't be the first time Diablo IV has been referenced as being in existence. Rumors circulated last year that Blizzard pulled a Diablo IV trailer at the last minute. Originally reported by Kotaku, they can confirm a video was made, but not that it was meant for Blizzcon 2018.
Either way, it's entirely possible to see Blizzard officially announce Diablo IV at their annual conference this year, which likely will be an interesting one thanks to all of the current controversies and protests going on around the gaming giant. We'll be in attendance at Blizzcon and will definitely be reporting on all the games and events at the show.