Granted, it depends on how it turns out. But my first impression is that authoritative reference documents of MDN are going to become cluttered with comments and disagreements.
I change, I publish, it's done. And if my change was wrong, or opinionated, or bad, it's just like that until somebody else catches it and fixes it back.
It seems to me that as far as the browser makers are concerned, MDN is as close to authoritative as you can get without going to the standards documents themselves - and the standards don't give you browser compatibility matrices or make any note of browser-specific quirks.
MDN may be a wiki, but it certainly isn't treated like one by the people who are most interested in it being accurate and up to date.
"Authoritative reference documents of MDN are going to become cluttered with comments and disagreements"
Which suggests previously authoritative docs are becoming less so due to being editable. I'm just pointing out they are and always have been subject to edits from the public. If anything the PR process will likely increase the reliability of the info because there would be a chance to do some vetting of changes.
I totally agree that MDN is as close to authoritative as you can get, but it's one (important) step away.
Every recent review I've seen of Wikipedia vs arbitrary big-a Authoritative sources has said that both have issues and overall Wikipedia is better.