From that link: Once Mir’s support for Wayland clients is on a par with the support for “native” Mir clients we will likely phase out support for the latter.
Does that mean they want to phase out Mir once they have a full Wayland display server? I thought the whole point for them was to continue to support those that are already using Mir? This still doesn't make any sense to me.
I thought one of the original distinctions was that Mir was going to work with the old closed-source nVidia driver, while Wayland insisted on doing it the "right" way and made nVidia catch up instead of pandering to them. Other than that, I've never heard anything to justify Mir's existence. Why not just start with an existing Wayland server that supports all the features and move on? They'll reach the end goal faster.
I'm not trying to be negative, but if the end goal is to be a Wayland display server then why is it so hard to let Mir die? Is it just pride? Separation Anxiety? ;-) j.k. but really what is it?