What we know so far:
122 kingdom cards (12 previewed w/1 Victory card)
31 Spirit cards (Imp, Ghost, Will-O’-Wisp)
12 Boons
42 Heirlooms
1 State
33 Randomizers
That’s 241. We’ve got 21 kingdom cards not yet previewed so that’s likely at least 210 more, putting us at 451. So what are the other 49?
Surely there are a few more states, and a few of the kingdom cards may be 12-card piles (or more). But that can’t account for too many, unless we get a couple new Traveler lines as some have speculated.
Somebody speculated there will be 13 different Spirits, each with a unique number of copies (1 to 13). If so, the 10 Spirits we haven’t seen will total 60 more cards, leaving 22 for the states and extras for Victory cards.
There may even be some kind of Traveler-Spirit line with a kingdom card that gets upgraded but instead of 5 of each upgrade, perhaps there will be 5>4>3>2>1 or something like that. The life story of a Spirit? Maybe.
I believe Hexes were in the original expansion announcement, which might be the anti-Boon triggered by Cursed Village or something else? Looking forward to two more days of previews.
Edited to include Randomizers.