Fedora is moving everything from /bin, /sbin, /lib, and /lib64 into /usr because maintaining this separation no longer really makes sense: http://www.freedesktop.org/wiki/Software/systemd/TheCaseForT...
However, that's not to say that we haven't arrived at similar conclusions (a root filesystem accessible at boot, multiply hierarchies of additional storage under, say, /usr, /usr/local, etc.
I mean, the ultimate conclusion of the UsrMerge argument would be to put all directories on root.
I find the justifications for UsrMerge to be specious at best, and better described as counterfactual. I strongly suspect that a large part of the reasoning is Red Hat's chronic inability to enforce discipline among its software packagers (both within and outside of Red Hat).