The new version comes with the following changes:
X is now rootless with the help of systemd-logind, this also means that it must be launched from the same virtual terminal as was used to log in, redirecting stderr also breaks rootless login. The old root execution behavior can be restored through the Xorg.wrap config file (man xorg.wrap). Please note that launching X through a login-manager (gdm, kdm, ...) doesn't yet provide rootless access.
The default configuration files are now in /usr/share/X11/xorg.conf.d, all host configurations are still taking place in /etc/X11/xorg.conf.d/ directory. Please note that files 10-evdev.conf and 10-quirks.conf in /etc/X11/xorg.conf.d could be renamed with .pacsave suffix, which could break your configuration, then just rename them and remove the .pacsave suffix.
Better glamor accelerated rendering, deprecating
A new package
xorg-server-xwaylandthat allows running X applications inside a wayland session.
xf86-video-intelpackage doesn't provide dri3 support anymore because of multiple rendering bugs.