There are Anima that you can earn in WoW Shadowlands, but it is not a lot. This isn't a huge problem, as cosmetic items can be purchased for Anima and developers say there's no need to have everything right away - players have the entire expansion time to unlock all. Anima's income has increased significantly in the past because of the responsiveness of Blizzard.
This is possible thanks to the bonus Anima that you receive when you upgrade your Pact Sanctum. Depending on how much you have upgraded the four facilities, you will receive the achievements Out Of the Ruins and Drought. What is drought? Sanctum Sanctorum, which increases the amount of anima you get. You'll receive more Anima items if you defeat a raid boss, or complete a quest in the world.
- The bonus anima are tied to achievements, not actual Pact Sanctum upgrades. They won't be lost if you run out of upgraded Sanctum.
This applies if you cancel your pact. You will need to rebuild the sanctum from scratch. You will still receive the additional anima.
You might consider buying upgrades to your sanctum if you plan on changing your pact soon. This is because you won't have the ability to take the anima from the reservoir with you anyway. This will give you an increase in anima income when you start your new pact.