While its true that a new "WM" in wayland would be a diffent binary its not really the same as a different X server. All the stuff that X does wrt hardware and stuff is not really in the wayland compositor, but in the drivers, and they are the same with both WMs.
And the WMs would link to the wayland server library, so a lot of code would be shared between them.
I don't think properietary drivers need to have their own wayland server. However, they do need to add EGL support, so that wayland can use the driver outside of X, and a few specific GL extensions that wayland needs. See e.g:
http://ppaalanen.blogspot.fr/2012/03/what-does-egl-do-in-way...
And the WMs would link to the wayland server library, so a lot of code would be shared between them.
I don't think properietary drivers need to have their own wayland server. However, they do need to add EGL support, so that wayland can use the driver outside of X, and a few specific GL extensions that wayland needs. See e.g: http://ppaalanen.blogspot.fr/2012/03/what-does-egl-do-in-way...