Patch 9.1 titled Chains of Domination for Shadowlands will be heading onto the Public Test Realm (PTR) in two weeks. Check out the forum post here. We are guessing from the announcement to move to PTR in two weeks we will be having an early summer release of the content pack although an official release date has yet to be announced.
This is a first major patch for Shadowlands, and it's going to put in a lot of content ranging from a new subzone in The Maw called Korthia, a new raid called the "Sanctum of Domination" which will feature ten bosses including Sylvanas Windrunner! Of course it also boasts new story quests and a Covenant campaign and a new eight boss mega dungeon to run through. You can view the full update in the video below: