> On future touch screen laptops (and desktops!), Shell will be quite nice,
No one has shown yet that touch laptops and desktops work. In fact, Apple did research in this area, and concluded that it did not work. Which is not surprising, because controlling a vertical surface is very tiresome.
> It just isn't particularly good at replacing GNOME 2, but there are others doing that. Mate continues GNOME 2 and XFCE and KDE both can provide a very-close-to-GNOME-2 experience.
It's saddening to see how far some in the free software community are removed from actual users. The average user who wants to get work done, is not interested in learning another desktop environment, they (reasonably) expect to be able to continue to use whatever they use with evolutionary changes. Mate is nice, but no company or organisation in their right mind is going to deploy a software project that is so fundamental to the desktop, that may not exist anymore in one or two years.
Our university is in this situation: it has hundreds of GNOME 2 on Ubuntu users. They cannot just switch to another desktop experience overnight (so, GNOME 3 and Unity are probably out), let alone, force users to switch to another desktop. They cannot install Mint (the usual answer you'll hear around here), since they use Canonical's Landscape management system and Mint is not yet an established player let alone a commercial entity where you can purchase support. tl;dr: they are between a rock and a hard place.
GNOME (and Canonical) probably have not realized what situation they have put large users in by not providing a reasonable migration path, or even beter, evolutionary development. The net result will probably be that some organisations will stick for years with LTS versions of Ubuntu (or RHEL), which sucks for other reasons (hardware support, old software). Others will seriously consider Windows, since, besides its flaws, Windows 7 will be supported for almost forever. And Windows applications will also support Windows 7 for many years to come. Where people have a choice of choosing their platform, some will switch to OS X (in fact, I see this happening in our university all around me).
tl;dr: the average user who is not interested in desktop environments or FLOSS, but just wants a decent workstation system, does not want to switch desktops, distributions, or user interface paradigms overnight.