I think Apple will have a very hard time arguing that the "reasonable" amount is a percentage of revenue with no cap.
It should be based on the app size, so maybe developers will stop shipping apps with a single feature and one button that takes 700 MB because of random bloated third-party SDKs that aren't even used.
They absolutely will and they will absolutely get away with it. It just won’t be anywhere close to 27%.
There has been craploads of litigation about “Fair, reasonable, and non-discriminatory” licensing over the last two decades, and fees that are percentages of revenue with no cap have survived and there is no reason to believe any of these legal standards will change.
In fact, I think it’s likely that Apple and Google will team up to create a standards body that defines the method for distributing/installing smartphone apps (because this is now in their best interest, not that I want them to). These standards are going to end up using a bunch of patents that you will have to license on FRAND terms.
Yes, the cost is going to go down. Yes, Epic is going to benefit a lot more than any indie developer. Such is life