Manufacturers aren’t going to ditch Google. Play Store and Google certification are too valuable for them.

If legislation is made such that eg.: in the EU phones can not be registered in the cellular network unless they are open to both normal installation of apps (sIdElOaDiNg) and being able to fully install or remove Google Services, then Google will have to deal with who would want to work and pay to get a certification that effectively blocks you from selling and operating in one or more continents.

And such legislation would be not without precedent: open phones and custom ROMs are already suffering from it.

What’s good for the goose is good for the gander.