Apparently there was a writing of "The Prophecy" in the 2019 book Master & Apprentice, which is considered canon:
"Only through sacrifice of many Jedi will the Order cleanse the sin done to the nameless.
The danger of the past is not past, but sleeps in an egg. When the egg cracks, it will threaten the galaxy entire.
When the Force itself sickens, past and future must split and combine.
A Chosen One shall come, born of no father, and through him will ultimate balance in the Force be restored."
Which I know they were writing it after the fact to make it fit the Prequels, but it kind of spells it out pretty clearly that a bunch of Jedi were going to die before "balance was restored", but maybe for most of the Jedi this prophecy was so old that it was like a myth or a fairly tale that many just assumed would never come to pass. It almost seemed to be that the extinction of the Jedi AND the Sith was the "ultimate balance", but I doubt they'll give up the ghost of the Jedi just like that. Not sure where Disney will go with it, as they're meandering pretty slowly through the timeline, though the next SW movie with Rey ~~Palpatine~~ Skywalker is supposed to take place 15 years after Ep IX, so I guess they're finally moving to push things forward.