Well, you can tell if your users start complaining--Gnome 3--or your products aren't successful.
Users of Gnome 3 are being very vocal with genuine (and some not-so-genuine) complaints about how the design process is going and what the final product is like. Since the Gnome guys are now in the cult of design dictatorship, they are always right no matter what--even at the expense of their own users--and their users are wrong to complain. The result will be an ultimately failed product. (I would bet money that at some point in the next 2-5 years Ubuntu will fork significant parts, if not the entirety, of Gnome--and when the 500lb gorilla picks up his toys and leaves, the game's over.)
Yes, a product must have some kind of vision, and at the end of the day someone's got to implement it, regardless of their talent. But humble designers recognize complaints and the needs of their users. Design dictators ignore them, because the dictators are by definition always right. That's a bad attitude to have, because most designers aren't perfect--but the human ego loves having control and loves being right. When people are told that success means being opinionated, it's a very easy thing to agree with, because everyone thinks their own opinions are the best.
I would bet money that at some point in the next 2-5 years Ubuntu will fork significant parts, if not the entirety, of Gnome...
The replacing of Gnome has already begun. They replaced Gnome Shell with Unity and GDM with LightDM. They're using Qt more often now as well (I believe Ubuntu One is Qt and I know that Unity2D is too), so it seems that perhaps GTK+ will be next.
They are, in server-side stuff--but not in desktop stuff, which is what Gnome 3 is specifically targeting. Ubuntu is far and away the largest desktop distro, so losing their support would be a pretty big blow to the adoption of the Gnome project as a whole--regardless of who's funding it.
This is becoming even more true as Steam will probably only support Ubuntu. Games are where the desktop users are. Gnome can spin its wheels and bask in its own self-righteous awesomeness but if the users aren't there, then it's all for nothing.
Canonical has the larger userbase, but their development work is pretty limited- basically, they do the Unity shell and their app-store. Most desktop related development (hardware support, DBus, core desktop libraries like PolicyKit, GTK+) happens inside Red Hat.
If they want to offer better binary compatibility between releases... well they can't, because they don't employ those guys.
If they want to support a new OpenGL release... well they can't, they don't employ those guys.
Ubuntu is crazy popular, but people really underestimate the extent to which they are an epiphenomenon.
Ubuntu conveniently distributes and packages desktop Linux. The software that they distribute may be written by a person employed by Red Hat, but I don't care. I just want to run a version of Linux that is easy to use, configure and upgrade.
>This is becoming even more true as Steam will probably only support Ubuntu.
Has Valve said that they will only be supporting Ubuntu, at the moment they are still in a private beta for the initial port to Linux, and if it goes well I suspect that we will see Valve support steam on non-Ubuntu systems. Even if they do not officially support other systems, I suspect we will see people make on-official ports.
RHEL 7 is based on Fedora 18, and will ship with Gnome 3.6 including the shell as default. It will be interesting to see how many corporate clients start using fallback on their desktop clients... and I saw a note somewhere that XFCE may be made available in the RHEL 7 repositories.
I say this as one currently using Gnome Ubuntu Remix on a couple of machines to see what 3.6 is like - its actually quite nice in my opinion.
My gripe is not with Gnome removing features that are useless, but with Gnome removing features that are useful just to influence user behaviour.
The case I have in mind is the lack of an option to leave the screen on even when inactive for a long time, because the developers want to discourage that power usage pattern (https://bugzilla.gnome.org/show_bug.cgi?id=647828). Typically users do not need to leave a screen always on, so the default behaviour should not be to leave the screen always on, but if a user needs to leave a screen always on for whatever reason, why should they have to install an extension?
It is the Gnome designers' job to design the system to their taste, but it is not their job to try to influence the users.
Those "sparse resources" were busy removing functional code such as the location toggle button. Ironically, this caused many hours of discussion, time in which those "resources" could have been doing something else.
Often the functionality removed was very useful. Want to keep your screen on all the time? Can't - you have only got an hour. Write an extension or patch the program to get around the issue (VLC). Want beautiful screensavers? it was removed, and needs to be reimplemented. What was that about not taking up the time of scarce resources again?