Haven't seen anything here yet, but Hearthstone Top Decks has a list for cards rotating in/out for 2022.  If accurate, I think I only counted 1 Epic, 4 Rares, and 2 Commons rotating out that were Core '21 specific.  So if you want them it's either a) not a huge dust investment to craft or b) if they are added to the Legacy packs should be easy to obtain if you already have all the Legacy cards.  Open a few packs and you'll likely get most of them.

That said, are they being added to Legacy packs?  I can't remember.

UPDATE: Looks like the team is working on it.  In the Cards search page you can select Core 2022 as a set.