I wasn't pointing to protocol stability as a SF feature, just as a "it sounded like Wayland was only recently declared 'done'", but I haven't followed Wayland development very closely, so it's possibly I completely misunderstood things here.
First public exposure to SurfaceFlinger would be Fall 2007 (SDK preview release and emulator) and first code drop would be Fall 2008 (Android 1.0 and G1 launch), but it's certainly something that was there from the very early days of the platform -- possibly late 2005, but certainly early 2006.
The hwcomposer HAL actually aims for some level for forward/backward binary compatibility (to ease development and upgrades), and while it doesn't reach back to the early days of SF (which has definitely evolved over the years), I just this week have been writing some test code for the HWC HAL that happily runs on a variety of devices from different OEMs and with different versions of the platform.
I'd be pretty doubtful about us shifting away from SF (especially now that hwcomposer and sync support is looking pretty solid), but we certainly are willing to pull things up and rebuild if necessary -- though the other commenter with his bluetooth complaint may be actually arguing *against* that, I guess.
From the other direction, though, unlike the earlier (now abandoned, I gather) work to stack Wayland on top of Android underpinnings, the hwcomposer HAL provides a much more flexible and richer surface than the old fb HAL, which certainly should be useful to the Canonical folks with their Mir compositor, as well as to anyone wanting to revisit a Wayland-on-Android world, though in both cases I'd assume the goal would be to get access to a wide variety of hardware ready to run "out of the box" rather than to actually use much of Android.