In the German magazine Gamestar an advertisement appeared where you can see a book of artworks, The Art of Diablo, which, according to the translation, includes works from Diablo I, II, III and also Diablo IV. The book, preordable only on Amazon Germany at the time, it was made by Jake Gerli with the supervision of Robert Brooks, senior Blizzard employee.

Diablo IV
One of the pages of the book Art of Diablo

With the Blizzcon at the gates, the announcement of Diablo IV may be imminent, in addition to other projects related to the franchise as the mobile title Diablo Immortal.