Sorry about that inconvenience. The current plan is to revisit WebSocket debugging in Q1 next year, per https://bugzilla.mozilla.org/show_bug.cgi?id=885508.
Part of the delay is the complete rewrite that most of the DevTools are undergoing. As we move from legacy, in-house solutions (XUL) to standard web technology (HTML/JS, React/Redux, etc.) as part of the "devtools.html" project: https://github.com/devtools-html/