Yes, FF Beta is a universal app. You can sort of follow along with development but I don’t know how what’s over there translates to the beta being deemed ready for production. It’s a good sign that it’s into beta from nightly already, though. https://bugzilla.mozilla.org/buglist.cgi?quicksearch=apple+silicon
(If you’re seeing nightly or beta still showing as Intel, just manually replace the app instead of relying on the updater. It seems like a lot of programs are like this.)