The original plan with Ubuntu 13.10 was to ship Mir as the default display environment for supported configurations (those using open-source Intel / Radeon / Nouveau graphics) and then to fallback to a traditional X.Org Server for unsupported configurations. Only a few weeks ago it was decided not to use Mir on the Ubuntu 13.10 desktop as it's not ready yet to replace the X.Org Server in production environments aside from some mobile use-cases.
Under the goal of having Mir by default for supported configurations in Ubuntu 13.10, with Ubuntu 14.04 LTS they would then have XMir as the default with no fall-back support due to having full Mir driver support. In Ubuntu 14.10, it would be the native Mir stack with rootless X legacy support and the Mir-native Unity 8 interface.
With having Mir postponed by default for Ubuntu 13.10 (and only being available as a post-install option for those to install the extra packages), it will be very interesting to see how the situation plays out for Ubuntu 14.04 since it's a Long-Term Support release. Modern Ubuntu LTS releases are maintained on the desktop for a period of five years so generally Canonical is conservative with pushing major user-facing changes into these versions.
Beyond the skepticism by many that it would be odd for Canonical to ship Mir by default in Ubuntu 14.04 LTS, a blog post by Canonical's Rick Spencer doesn't give too much hope for the next LTS release.
Rick Spencer, the Vice President for Ubuntu at Canonical, wrote a post today entitled Rick's Ubuntu for Phones FAQ. In the post he made interesting comments about Ubuntu Touch and Canonical's new mobile ambitions, which were interesting, but what I found most interesting were his Mir comments.
The Ubuntu Desktop has always depended on implementations of the X11 protocol (xorg). This technology is more than 20 years old and designed for very different systems than are available today. Between the complexity of the protocol and the drivers, it is a significant effort to deliver a stable and fast system to end users. Even with this effort, their systems sometime regress or break, especially if the users are using drivers from their GPU chip vendor. Writing a window manager on top of this protocol also turned out to be very complex, often due to differences in the implementations of APIs in the GPU drivers, and also due to complexities in the X11 protocol.
The Mir display server solves these problems by offering a simpler and more direct library to both GPU driver developers and Window Manager authors. Mir is also designed to work easily with existing Android drivers.
The Mir display server on Ubuntu for phones is carefully designed by the Ubuntu design team, and takes advantage of the simpler more direct Mir API to deliver faster development and a better user experience.
Mir display server and window manager are currently optimized for phones and to some degree tablets, but will grow over the next few releases to provide a full desktop experience as well.
What I found most interesting about that were Rick's ending comments in that it would grow over "the next few releases" for providing a full desktop experience on Mir... No mention was made about shipping Mir for the desktop in the next release, 14.04 LTS.
So I will bring it to the always insightful and controversial forum goers, do you think Mir will make it to the Ubuntu 14.04 desktop by default? It will be very interesting to see what happens. While some think I am anti-Mir, I am simply in support of advancing any solution to advance the Linux graphics subsystem to better compete with the proprietary and dominant operating systems while providing a superior Linux desktop user experience.