Good abstractions aren't about predicting, they're about being nimble so that when change does come along, it's easy, because you don't have a ton of duplicatio

Good abstractions aren't about predicting, they're about being nimble so that when change does come along, it's easy, because you don't have a ton of duplication to fix in order to change the abstraction. The new business rules don't belong in the abstraction in general anyway, they belong in the concrete implementations, that's the point of having implementations.