I am not sure about the "I don't see that changing". CD projekt red has adopted unreal engine leaving behind the engine they built AAA games such as The Witcher 3. I can see a future where more gaming houses adopt the engine as well.
For CD Project the move to Unreal might make sense just from labour market perspective - it’s easier to hire programmers for Unreal than to train programmers to learn and develop your own in-house engine. Larger community and support already exists for Unreal etc. That move will affect their bottom line on their next games though. 5% is nothing to scoff at for a big product from a big company.
In any case, I’d advise caution to companies relying entirely on a single platform for their business. To echo my previous statement choosing only between Android and iOS for mobile is an illusion of choice. If you’re a mobile game dev your entire business relies on two relatively hostile companies.