That was certainly a concern. When instrumenting PHP to detect where the behavior changes and testing various codebases, I found that this actually happens much more rarely than I would have anticipated in advance. We're talking like 2 occurrences in the test suite of major frameworks.

Strict types (scalar type hints for method signatures) have been around since PHP 7, and since then I would say it is recommended to always use === (with type check) over == (no type check) so one would have enough time to upgrade it‘s code.

And it also just makes sense from the language design perspective to fix that behaviour. Having a major version coming is a good time to fix such stuff imho.

Strict comparison operators have been considered best practice since well before 7.0