Won't the new GNOME 3 classic mode effectively render Cinnamon, MATE,
and friends obsolete?
gnome-classic-session is in Rawhide and I expect it will satisfy some users but not at all. In particular, there are people who can't get enough performance out of software rendering in GNOME Shell and have to use something like MATE for the time being. Also, while the UI in classic session is quite similar, it isn't exactly the same (ex: workspaces, applets etc).