The latest World of Warcraft subscriber numbers, revealed as part of Activision Blizzard's financial results for the third quarter of 2015, have slipped once again, albeit quite slightly, to 5.5 million subscribers. That's only—"only" being relative—a drop of 100,000 users since August, but even so, this report represents the end of an era.

Not because of the number itself, mind you. World of Warcraft remains top of the subscription-based MMO pile, and "players are excited about the upcoming expansion, Legion, which will feature a new class, customizable Artifact weapons, class order halls, and much more," Activision said. But as reported by GameSpot, WoW subscriber counts will not be made public in the future.

"Note that this is the last quarter that we plan to provide subscriber numbers," the company said. "There are other metrics that are better indicators of the overall Blizzard business performance."

Those indicators will apparently be measured in "engagement," a porous sort of term the studio already seems quite fond of. Hearthstone's "key engagement metrics" have grown 77 percent year-over-year, for instance, while Black Ops 2 engagement has increased as well, despite being three years old and unavailable on current-gen consoles.

World of Warcraft still has plenty of legs—5.5 million subscribers still adds up to a hell of a pile of money every month—but the Legion expansion, announced in August, looks set to mark the end of an era, too. Find out why here.