I see the same crash since my last package upgrade (today). And it affects not just kate, but _all_ of KDE 5: plasmashell, sddm, konsole, you name it. The crashes produce different backtraces sometimes, but in general, it happens after xcb_intern_atom or XInternAtoms. konsole still uses KDE framework 4 AFAIK, so it calls out to libx11, not libxcb.
Could this be a bug in Xorg?