After reading Stinger's thread I posted a note here:
http://ubuntuforums.org/showpost.php?p=12336188&postcount=91
But in hindsight I decided that conversation more properly belongs here :)
Just read on the ubuntu-desktop mailing list:
Seb, I blame the remix idea on you. ;) Anyway, if the GNOME remix
becomes an official flavor, I was hoping to then ask for permission to include the GNOME3 PPA due to our unique overlap with the flagship Ubuntu release. It's still a bit of a handicap as I don't think we could gain that trust if we included things that regressed Unity.
If we don't fork ubuntu-control-center and ubuntu-settings-daemon off from gnome-control-center, then I don't believe it will be possible to ship GNOME Shell 3.7/3.8 next cycle. The last two cycles we've shipped the latest GNOME Shell but with bugs due to incomplete g-c-c/g-s-d support in Ubuntu (for 12.04 it was http://pad.lv/965921 with keyboard shortcuts not able to be configured from System Settings and for 12.10 it was 1045914 with a missing keyboard layout status menu). [B]It's a reasonable guess that for 3.8, the GNOME developers will move aggressively to kill fallback mode[/B] and make optimizations and GNOME Shell will depend on those newer optimizations.
A big reason for the GNOME remix is to show that you can contribute to GNOME from Ubuntu. I worry about what happens when most users are using a different distro than most developers. Shipping an outdated GNOME means that we have a much less compelling story to tell these developers.
So once the UDS dust settles I'll ask Jeremy if that means metacity and gnome-panel will be dropped altogether.
Edit: I found this after a bit of googling:
http://worldofgnome.org/gnome-3-8-fallback-mode-the-first-feature-under-discussion/
In one of the later comments Jeremy says:
He means if you don't have working 3D, then Totem won't work.
Now that we have llvmpipe, it doesn't seem like GNOME needs a "fallback mode" for when GNOME Shell won't work. [COLOR="Red"]I think gnome-panel should be allowed to continue as GNOME Classic instead of as GNOME Fallback.[/COLOR] In other words, getting rid of some of the patches that made it look like GNOME Shell even though most of its users would prefer it look like a polished GNOME 2 desktop.
It sounds like there is also a need for developers to continue updating the code to keep it on par with the latest GTK3 and GNOME 3 code. This is the project the Mate developers should have taken on.
I definitely agree with that sentiment.
I personally hope that plain old metacity survives because I find "classic (no effects)" to run just as efficiently as Lubuntu on lower-end hardware, but it's not a huge deal.
And I've come to really like the new gnome-panel, it "just works" :)