I assume they didn't mention nix for the simple reason that RedHat and Debian and other distros aren't going to give up their own packaging setup. So the only way forward is to work with what you have.
Err, what the blog entry describes is just as disruptive to the deb/rpm setup as what nix is doing.
Heck, i think with some clever symlinking you could in theory dump a rpm into its own (optionally versioned) subdir and still have it working in the grand scheme of things.
The biggest stumbling block for current package management is that of versioned libs. Usually they work around this by putting different package names on different major lib versions.
