Don't make a mistake, systemd is not (just) an init system. It's a replacement of more and more Linux userland. I suppose later on it will replace much of the filesystem, network, and process security management tools, stuff like xattrs, ip / ipfw, and selinux.

I suppose that the end goal of the systemd project is an ability to deploy a production Linux system with just systemd and busybox, and run all software from containers.

Not that it's a bad thing to strive for. But it's not going to be Unix as we know it.