Not sure if my (small) company is a representative RedHat customer but we do have several tens of RHEL workstation and most of our software vendors have standardized on this distribution.
At the moment it is impossible for us to switch to Gnome 3, we have encountered too many compatibility issues with our legacy software, and we would have to sacrifice support of our vendors (unofficially they do permit some minor deviations from the environment they specified but that's not going to happen for Gnome 3).
Not sure what we will do once Gnome 2 is discontinued - hopefully RedHat will find a suitable replacement (from what I've seen Xfce would be fantastic - much better than our current Gnome 2 desktops). Or, maybe our vendors will start supporting a wider range of distributions or will come up their own.