I don't think Apple will diminish their control on the App Store requirement, it's too much of a selling point to them. In fact I hope they keep their requirements the same, and I'm quite happy to see sideloading becoming a thing. More choice is nice.

I'd be so happy to see F-Droid venturing on the iOS side, and distribute open-source apps you can trust that would otherwise not be available on the App Store (emulators, third-party YouTube clients, an actual Mozilla Firefox browser using its own rendering engine, etc).