When Qt und GTK focus on Wayland, these DEs will have native Wayland applications, and X will not be a first class citizen any more. It will only be supported as an legacy interface. As long as we don't want to be stuck using current software versions, that means that de-facto Wayland *will* replace X11 in the medium-to-long term.
Besides, the experience of running X11 on Windows or OS X is no good advertisement, either. I've done both, and good integrated support is something different.