I think this is unlikely. Mac gamers need Unreal more than games developed using Unreal need Mac users. Mac is an incredibly niche market for games - they're not going to rewrite their game using a different engine to run on Mac, and Apple knows that.
Of course, Apple could decide they don't give a shit about native Mac games, why don't you play our iOS games, but that just seems petty.
I think it's possible to make persuasive argument that this already took place around the time that they killed OpenGL support and/or refused to allow Vulkan support. Requiring a proprietary API that only works on a tiny subset of gaming devices* seems like they've already made their position on this topic very clear.
* I'm excluding mobile devices here since mobile games were called out as a different market in the parent comment.
The relief to which Apple is entitled is that to which Epic Games stipulated in the event that the Court found it liable for breach of contract, namely:
(1) damages in an amount equal to (i) 30% of the $12,167,719 in revenue Epic Games collected from users in the Fortnite app on iOS through Epic Direct Payment between August and October 2020, plus (ii) 30% of any such revenue Epic Games collected from November 1, 2020 through the date of judgment; and
(2) a declaration that (i) Apple’s termination of the DPLA and the related agreements between Epic Games and Apple was valid, lawful, and enforceable, and (ii) Apple has the contractual right to terminate its DPLA with any or all of Epic Games’ wholly owned subsidiaries, affiliates, and/or other entities under Epic Games’ control at any time and at Apple's sole discretion.
This may very well kill Epic's Unreal Engine business (at least on Apple platforms) if they no longer have the necessary licenses to use Apple's developer tools.
The logical ruling would be to force Apple to pay reparations to all the app developers that they have illegally forced to pay for the app store.
From the ruling (page 172):
> In California, “where a single contract provision is invalid, but the balance of the contract is lawful, the invalid provision is severed, and the balance of the contract is enforced.”
In other words, even though the judge found the anti-steering provision of the contract to be illegal, the rest of the contract was still legal and enforceable, and Epic violating the other terms of the contract entitles Apple to damages.
Edit: Note that this a descriptive statement regarding the ruling, not a normative statement of my opinion.
> a nationwide injunction shall issue enjoining Apple from prohibiting developers to include in their Apps and their metadata buttons, external links, or other calls to action that direct customers to purchasing mechanisms, in addition to IAP
Obviously this would seem to imply that developers are allowed to accept payment from alternative systems to unlock digital content in apps. But it doesn't explicitly say that. All it explicitly says is that developers can link to alternative payment systems. I hope the actual injunction is more explicit.
So, Apple was in the wrong about forcing app devs to use their payment processor (and taking a 30% cut at the time - 15% or 30% now), and they have to change that.
But Epic was also in the wrong when they tried to go around this rule, and they have to pay 30% on every transaction they made after their update in which they used direct payment?
But if Epic didn't try to go around the rule and loudly complain, there would be no judicial case, and no ruling forcing Apple to change?
This is weird to me.