With the introduction of Amirdrassil in Dragonflight Patch 10.2, Great Vault thresholds have also changed! Unlocking raid reward choices now requires 2, 5, or 7 boss victories, as opposed to 3, 5, or 7 in Aberrus, making it slightly easier to earn the first vault reward.
The current vault requires 3/5/7 Aberrus raid bosses, while Patch 10.2 will be reduced to 2/5/7 from Amirdrassil.
While this is undoubtedly a good change for players looking to easily unlock a raid vault reward, it's not all great news, as it also means unlocking all three choices requires a full clear of the new 7-boss raid — giving raiders no potential to sit or switch out with another player, which is common in many dedicated raiding groups seeking to rotate players in and out as needed.
Mythic+ and PvP thresholds appear unchanged at 1/4/8 dungeons and 1250/2500/5000 Honor respectively, although Blizzard Assistant Game Director Morgan Day and Senior Game Designer Patrick Scarborough commented on increasing availability of Mythic+ rewards in an interview with MrGM yesterday, stating that Heroic, Timewalking, and Mythic+0 dungeons will also populate the Great Vault, unlocking reward slots the same way.
The Vault is intended to still contain the same Seasonal rewards, even if Timewalking dungeons are done to unlock them, but it should help players doing lower difficulty content and weekly quests like A Frozen Path Through Time still earn weekly rewards.