I don't think MDN is going to go anywhere anytime soon. I remember someone on Twitter saying that there are enough people from other organizations who had already been involved in the MDN docs before the lay-offs at Mozilla and that these people will likely stay involved.

Case in point: Both the MDN Github repos and the MDN docs (or at least all the pages I bothered to look at) show very recent activity:

https://github.com/mdn/

https://developer.mozilla.org/en-US/docs/Web (scroll all the way down to "Last modified")

https://developer.mozilla.org/en-US/docs/Web/CSS

https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re...