Yeah I've been following developments about Mir too....
They risk marginalising themselves big time, but it's too early to cast full judgement, they haven't ruled-out active collab. with Wayland/Weston, or even merging efforts longer-term.
But if Mir's mostly/totally closed/proprietary, then there'll be lotsa anger in the wider community(s)...
They've also moved back towards Qt/QML instead of GTK+, they're re-writing all of Unity with it, great for the Qt biosphere overall, but not sure if it's great for them specifically.