This seems pretty big, like it should have an immediate impact with everyone who ever wanted to use alternative payments on any app store should be submitted an updated app today kind of big.

Are there strings like appeal rights that means we won't see a change for years?

This injuction only applies to Apple, as it says pretty clearly in the decision. That prohibition does benefit all developers using the App Store, not just Epic.

There is a good chance that this precedent will encourage other lawsuits that will lead to more injuctions, such as one that applies to Steam.