I had problems after upgrading in Nov 14 updates on my laptop and also Nov 20 updates on my desktop. Both showing same sympthoms, in which both failed to load X server, so i'm stuck at the console. I tried many things even reinstalling all packages using slackpkg, but no luck.
Today, my desktop had the same problem as my laptop after applying the Nov 20 update. So i tried to see the log more carefully, hoping to find a clue on how to solve it. Then i saw this line:
Using config directory: "/etc/X11/xorg.conf.d
Using system config directory "/usr/share/X11/xorg.conf.d"
I suddenly realized that the configuration for the new version should be placed inside /etc/X11/xorg.conf.d instead of /etc/X11. I saw 20-intel.conf on my /etc/X11/xorg.conf.d/ directory, but the content is a little bit different from /etc/X11/xorg.conf, so i tried to copy the value to the new file and my MATE desktop (on my laptop) is now back on action. I tried the same method on my desktop and now everything is back as it used to be.
If you happened to have X segfaulted after latest upgrade, you might want to move the configuration file to the new location and see if it works for you.