Ubuntu 13.10 Saucy Salamanader swiches to Mir:
It looks like Canonical’s plan is to install the Mir display server by default on Ubuntu 13.10 Saucy Salamanader, running with XMir, an X.org alternative from Mir.
So, Ubuntu 13.10 Saucy Salamander will have XMir on Mir, by default, but will also ship with a fallback version of X, for the computers not supporting XMir, while Ubuntu 14.04 LTS ditches the classical X server for good, and uses only XMir on Mir. Also, Ubuntu 14.10 and later will use Mir by default and get rootless support for the legacy X applications.
OK, so far so good, but XMir will only work with open-source graphics drivers (from Intel, Nouveau and Radeon), as the announcement states. To my mind, the big ideea is that the users with proprietary graphics drivers from Nvidia and ATI will use the old X server (X fallback) and the others will have XMir available. It is supposed to make XMir work also with proprietary graphics card, until Ubuntu 14.04 gets is released.
Ubuntu 13.10 Saucy Salamander (and Ubuntu 14.04) will land with the “old” Unity 7, because of its Mir support. It looks like Unity 8 will scratch the surface only on Ubuntu 14.10.
Kubuntu 13.10 Saucy Salamanader not switching to Mir:
While Ubuntu 13.10 Saucy Salamander intends to switch to Mir and XMir as soon as possible, Kubuntu 13.10 will continue to use the X server by default, and Lubuntu 14.04 may switch to Wayland. But Kubuntu has to suffer for Ubuntu’s changes, what happens if Kubuntu Desktop is installed over Ubuntu? The Kubuntu team has to find a temporary fix for this issue, until Canonical finds out a permanent solution.