According to WOWHEAD's recent interview with Rod Fergusson, the general manager of the Diablo series, the upcoming 29th season of Diablo III will be the last season with new content, but it will not be as content-rich as the previous season. Starting from the 30th season, the content of past seasons will be repeated, indicating that the development work will be fully focused on the next game — Diablo IV!
Diablo IV is scheduled to be released on June 6 and will be available on Battle.net / Xbox Series / Playstation 5 / Playstation 4 / Xbox One platforms. Players who pre-order the Deluxe or Ultimate edition can play the game four days early on June 2.