Ubuntu  uses  Wayland  as  a  default backend in Ubuntu 17.10. This is
  going to be interesting. Now, Fedora and Ubuntu  default  to  Wayland.
  Has the EOL of X11 finally come?

  Actually, I hardly think so. X11 has been around for such a long time.
  So much software has been written for it. It's going to take a  looong
  time for it to actually die.