I take it you mean the move to Wayland. 
X11 is being phased out, and the future for Plasma is on Wayland. It has already been the default display server for Plasma and GNOME for quite some time now.
However, not all applications support Wayland yet, and most notably those applications that aren’t specific to Plasma or GNOME — which includes most of the applications included with a typical Xfce install.
Furthermore, some people with Nvidia hardware are forced to use the older Nvidia drivers, and those don’t work well (if at all) with Wayland. So for those people it is good to have the option of X11 as the display server still available.
That said, if you are certain that absolutely nothing in your system still requires or depends on X11, then you should be able to remove it entirely. But unless you know your system in and out, I do not recommend it.
Your English is good enough. 