From a recent Chinese interview...
https://ngabbs.com/read.php?tid=19140553&rand=543
1. The new version has no new occupations and new races. What is the situation?That is the google translate equivalent of the first question. Blizzard states that there is no obligation for a new class (occupation) or race for every other expansion, and that the death knight is the class they focused on instead.A: You may have misunderstood us. Our World of Warcraft project team has no rules to say that odd-numbered versions will have new occupations, or even-numbered versions will have new races. We are choosing to launch based on whether the next version of the story is suitable for a new career. The current version of the new version of Shadow Kingdom is closely related to our existing death knight, so we chose to let the death knight Full race.