This was confirmed by Blizzard on their blog.
Snow storm released new information about the upcoming season of Diablo III. In an entry on its blog, the study revealed some of the expected news for the April 15
The title released in 2015 still had no improvements for the latest console generations. Until the version of the series X is the one that comes from One S
- Update 2.7.3: Updated resolution on Xbox Series X|S. On Xbox Series X the game will run at native 4K resolution and on Xbox Series S at 1080p.
You can find all patches and news directly on this link.