WoW is still an immensely popular game and Blizzard wants to keep it that way. Looking over player trends across the past 9 years since launch it’s easy to see expansions are what drives players to reinstall the game.
We find that expansions are what bring players back to World of Warcraft,” “We really want to get to a cadence where we can release expansions more quickly,” “Once a year I think would be a good rate. I think the best thing we can do for new players is to keep coming out with regular content updates.”