I don't read anything in that post that says this.
Am guessing you a referring to the "Also note that at that point we intend to move udev onto kdbus as transport, and get rid of the userspace-to-userspace netlink-based tranport udev used so far" quote.
Which would suggest that udev might stop supporting the userspace-to-userspace netlink-based transport in the future. However, unless I am mistaken, I don't think this means it will no longer work on non-systemd systems.