Blizzard has confirmed that today's PTR build for Eternity's End will be the final major update of the year, which sees the third round of raid testing including the first look at the Anduin encounter.
Blizzard doesn't announce a testing schedule for each patch but has given the update to players so they know no more content will be published on the 9.2 PTR over the next few weeks.
The team will still be working on the upcoming update and will make changes to the PTR as they are needed, but no new content or builds will be uploaded until the new year.
Today's build has many updates added to the PTR which include, upcoming raid testing, certain tier set updates, new Night Elf male face models, and chapters 6 and 7 of the new campaign.
Today's World of Warcraft: Eternity's End PTR Update Is The Final Update For 2021 Says Blizzard
This is expected over the holidays, and likely won't have a large effect on the release date of the patch, as it would have been accounted for when development began, and players can hope to see a big update when Blizzard returns to office after the holidays.
In the meantime, Blizzard has made all of Legion Timewalking available throughout December, which includes the Mage Tower and Legion Mythic+ Dungeons.
Two sets of raid testing will be held on Thursday the 16th of December, and the 17th where players will get a look at the final 4 bosses planned for testing unless Blizzard decides to test the final three later on in the testing period.
The PTR will still be playable during this time, so players can hop on during the holidays and get the first look at Zereth Mortis, and everything else coming in patch 9.2, Eternity's End.