A SoV’s purpose should be to be a

Even with Bitcoin being basically near-stable in terms of supply, and assuming an ideal economic model, it will reflect effectively the same as inflation or deflation in terms of prices of products.

People will lose or gain trust in Bitcoin, some products become harder to produce, some easier, etc etc… There is no reason to value or want Bitcoin except to pass it onto someone else, and therefore that will reflect to the value of Bitcoin