The matter of Linux hybrid graphics support was brought up today during one of the morning sessions at the Ubuntu Developer Summit in Orlando. Simply put, there isn't much Canonical will be doing in the near-term to better support this technology (then again they aren't a company known for their upstream engineering work), but they do hold out hope for the longer-term that there will be improvements.
For Ubuntu 12.04 LTS they are looking at potentially offering support for Ironhide, which allows for hybrid graphics on NVIDIA Optimus systems in "a somewhat seamless user experience", but hasn't undergone thorough review and some Optimus laptops may not even work with this community-spawned creation. The open-source Ironhide implementation allows the NVIDIA binary driver to be used, but it's performance still isn't as optimal as running a native X Server on the hardware. NVIDIA Optimus is a MUX-less configuration, but for notebooks that are MUX-ed they are looking at maybe adding some logic so the user can choose which GPU they wish to have associated with the screen.
Supporting the MUX-ed configurations is a mess due to needing to restart the X Server, dealing with some drivers not liking each other, X.Org limitations, etc. It's all long-term work that's being done upstream to hopefully improve the situation someday and while the X11 Server is still dominant.
Recently there was some work done by David Airlie in the first phase of GPU hot-plugging, which eventually may benefit such Optimus / multi-GPU configurations, but it will be a significant number of months before everything is ready to be merged -- that is assuming the work ever even gets completed.
So in the next six months for Ubuntu 12.04 LTS there isn't expectations for much to change aside from possibly making the Ironhide project easier to use in Ubuntu, but longer-term the Ubuntu developers will wait and see what gets done.
The notes from the hybrid graphics support strategy planning session at the UDS-P Orlando summit can be found via this Ubuntu.com page.