Not accurate right now. Firefox and Chrome spoke about this at EdgeConf this year, along with the remotedebug founder, and basically said "Please go forth and develop a shim layer common protocol in the community. However, all browser vendors standardizing to a common protocol would slow us down too much." Video: https://www.youtube.com/watch?v=tQG6PljqmLc#t=1013 (around this timecode)

Hear, hear. None of this needs to be a standard to show a web page so I'm personally happy to let developers hack on what lets them be more productive, and let browsers continue to innovate. It's way too early to get a committee process involved, and innovation will happen faster this way.

Actually this article points to the reverse happening - they build bridges to be able to connect to each others protocol to work around having to use a common protocol.