X11 Sandbox Mitigation

Is Whonix still using X11 for an X Window Server? Is there a timeline for switching to wayland or xpra?

Ask/check XFCE DE when they will have this feature.

related:

No timeline.
Not a priority. (about priorities)
Probably if/when Xfce supports wayland and that lands in Debian stable.

Unlikely since no desktop environment / Linux distribution is using it?