There are a lot of things worth addressing.
Gnome project (especially libraries like GLib/GObject, GTK) is a mature project with a lengthy history. One of the aims of GLib/GObject libraries is to provide C API that is bindable by other languages. Therefore the GTK library is already accessible from almost all most common languages. I am not that knowledgable about various GNOME projects, but I saw most GTK apps written in C, Vala, Python or JS.
Therefore I would say, that "Swift needs GTK more then GTK need Swift". I would also say, that Swift won't became mainstream amongst GTK developers since Swift is Apple owned and controlled language which would contrast with the philosophy of the GNOME project originating in GNU.
The Swift bindings for GLib/GObject, GTK
The GTK (and it's dependencies) is a huge codebase. The public API and documentation itself is hundreds of thousands of lines. Since all of the APIs are in C, you are free to use the GTK from Swift already.
The quest for more idiomatic Swift interface for GLib/GObject or GTK is a tough one. The most viable approach is to generate Swift wrapper for C APIs. This can be done already, since GLib/GObject libraries can take advantage of project called
gobject-introspection which (amongst many things) produces XML metadata files with extension
.gir files are distributed alongside with developer versions of GLib/GObject and GTK libraries.
There is already a project which generates
.swift interfaces based on metadata in
.gir files called gir2swift.
The gir2swift project GitHub - rhx/gir2swift: A simple GIR parser in Swift for creating Swift types for a .gir file is a part of wider initiative to provide GTK bindings to Swift developers know as SwiftGtk GitHub - rhx/SwiftGtk: A Swift wrapper around gtk-3.x and gtk-4.x that is largely auto-generated from gobject-introspection.
I am a contributor to both projects. The gir2swift already implements a lot of features but the project is (in my opinion) in dire need of refactoring to make it more Swift-idiomatic and understandable for wider audience of open source developers willing to contribute. If you consider contributing, feel free to contact me with any issue and I will try to help as much as I would be able to.
Better Swift support
I would say, that we won't ever be able to achieve as seamless integration of GLib/GObject into Swift as we are used to from CF/ObjC. The Swift language, being the property of Apple, was designed to be compatible with ObjC.
Even as "simple" task as bridging GType fundamentals and collections would be a major undertaking, not even talking about subclassing GObject class in Swift.
It is my opinion, that the first step towards that future is building a community around the SwiftGtk and gir2swift project. I don't think Apple is "going to give us GTK wrapper for free".