For now. Watch what happens when Mir ships:

1. Noone will use Mir because xlib apps and non-ported toolkits will fail miserably.

2. It will not get tested properly.

3. Release+1 with XMir will be shipped and Mir will be turned on.

4. All hell will break loose.

If it doesn't happen, I'll cook and eat my laptop.

The only flag waving so far has been "shuttleworth installed it on his dell and it worked ok for a couple of weeks with some problems".