Earlier this week there was the posting of a patch series with initial XWayland support for the X.Org Server, which should be merged into the X.Org Server 1.16 release that should happen around July. With this new XWayland patch series comes a new approach to handling this X11 compatibility layer to Wayland. In the past there was a XWayland module and modified DDX drivers were used to support XWayland with 2D hardware acceleration provided by the GPU's native driver. Now, however, Wayland developers have been working on making the XWayland code into its own DDX and just utilizing GLAMOR for having 2D acceleration via OpenGL.
While this approach makes the XWayland support universal and doesn't mandate the individual X.Org drivers (Intel, Radeon, Nouveau, etc...) be modified for this X11 support on Wayland, the new design doesn't work well for NVIDIA's binary driver.
NVIDIA's James Jones has come out to reaffirm the company's plans to support Wayland but this new design doesn't work well into the work NVIDIA is doing internally to support Wayland by their binary-only driver. James wrote in a new mailing list message, "This direction seems to conflict with our plans to continue running our DDX driver under XWayland. If we can't run our DDX, we don't have a path to support GLX direct rendering under Wayland. I know we don't have anything publicly available for Wayland at the moment, but as I've alluded to publicly a few times, we are actively working on support and this certainly throws a wrench into things."
The NVIDIA binary driver needs to be loaded in order to have GLX direct rendering support under XWayland for having OpenGL hardware acceleration. We'll see how upstream Wayland developers respond and whether they'll be able to make the necessary changes to accommodate NVIDIA's feedback.