[keithpeter]

My (limited) understanding is that Gnome includes Wayland as an integral component, and so reverting to Gnome as default desktop for 18.04 will preclude use of the Mir graphical server.

[snuxoll]

Also, one of the "selling points" of Mir was its ability to use Android drivers to make OEM adoption of Ubuntu Phone relatively easy.

If they're ditching mobile, there's literally no real benefit to Mir.