As many of you are probably aware, we are working on the Mir display server that is designed to provide a fast, efficient, and extensible display server across phone, tablet, desktop, and TV. Our ultimate goal is a fully converged Unity 8 running on top of Mir ready for the next LTS timeframe, and in 13.10 we plan on making our first step in that direction.
For 13.10 we plan on delivering Mir by default in Ubuntu Desktop with XMir (an implementation of X running on Mir) and our current Unity 7 codebase (the same Unity codebase that is currently in the Saucy development release).
This will be enabled for graphics hardware with Open Source drivers supported by Mir (primarily intel, nouveau and radeon). For binary graphics drivers (e.g. many NVidia and ATI cards) that don’t support Mir yet, we will fallback to the normal X server that we usually ship. This will mean that all users are well served in Ubuntu 13.10 and everyone will get the standard Unity 7 experience with feature parity with X (e.g. multi-monitor support). This fallback will be removed for Ubuntu 14.04. We are working with GPU vendors and partners to provide the required driver support and are confident to have this in place for 14.04.