We should make this change and we should not undo it later. This misfeature causes source compatibility breaks left and right, complicates type checking, and makes code counterproductively vague. It's a vector for users to accidentally use underscored initializers and unsafe APIs. And it runs counter to the direction of the language towards treating parameter labels as part of a function's name. Kill it with fire.
(Specifically, name without parentheses should only ever match nullary (zero-parameter) functions/methods/initializers called name. If they have any parameters, you should need to specify the parameter labels.)
Edit: It's worth noting that we can deprecate this kind of matching in any release, but we can only make it an error in a release with a new language version. (For example, Swift 5.1 promises full source compatibility with 5.0, so in 5.1 we could have added this as a warning but not as an error.)