Just a few minutes ago via Archlinux Hispano official twitter a news has come to me from the official website of Archlinux and is that the packages systemd y udev now they form a single package called systemd-tools which also includes some new tools.
To substitute udev For this new package we proceed to update the repositories and execute the following command:
pacman -Sf systemd-tools
Note the parameter -f since it has to overwrite some man pages. Once the installation is finished we execute this other command to verify that the startup image de Linux:
mkinitcpio -p linux
Once everything is finished, it is only necessary to install the updates of the packages that required one or both packages.