This is a cool move! At least Arch Linux and Fedora Linux have done this. A typical root directory listing will look like this:
lrwxrwxrwx. 1 root root 7 May 30 23:17 bin -> usr/bin
lrwxrwxrwx. 1 root root 7 May 30 23:17 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 May 30 23:17 lib64 -> usr/lib64
lrwxrwxrwx. 1 root root 8 May 30 23:17 sbin -> usr/sbin
The /bin, /lib and /sbin have been in the root directory since first Unix was released in 1969. Any modern Linux distro won't have and won't need that many partitions than the legacy *nixes used to have. The reasoning is in this discussion thread.
Arch Linux guys have a pretty complex update process. The classic pacman -Syu won't do it for you this time.
