I noticed quite a lot of Unity talk in WWDC this year, even helping developers add a11y to their Unity games, whereas Unreal Engine was not mentioned at all.
So I could see Apple adopting an engine like Unity to help build out their games and AR offerings.
SceneKit and SpriteKit have received very little attention over the past few years and RealityKit is still anemic in terms of features.
Unity could also be a weapon to wield against their newfound rival, Epic.
On the other hand, Unity would be an awkward fit into the Apple tech ecosystem because of its reliance on C#.
It’s also buggy as others have mentioned, but Apple has the resources to pay down their technical debt.