Earlier quoted context omitted.
From what I gather, Pipewire isn't part of Gnome, i.e. it's generic and can be used with any DE. For example, all compositors are using libinput, which replaces legacy ways of X handling input. It's not mandated by the protocol either. So I don't see why they can't use Pipewire for audio and video needs. If anyone wants to make a better alternative to standardize on - they are free to propose it.
But libinput is a freedesktop.org project, ie, supported by the same people who are working on Wayland. It was specifically built to support Wayland. Pipewire looks like some audio-visual framework for GNOME and GTK apps and while it might be fantastic it is both new and not very comprehensibly advertised. And it will probably be very complicated and involve some rather interesting design issues compared to building…
The wayland environment is maturing quite fast now.