I think it comes down to what the final DCC RPG product looks like and how compatible it is with existing products.
If it's based off of the 3E SRD, it's possible that one can use any monster book from 3E or Pathfinder. In that case there are already a large number of monster books out there.
If it turns out to be more like AD&D there are books there as well. (The full-color 2E monster book comes to mind.)
So after we see what it looks like, then we'd have to determine how a DCC monster book would differ from existing products. Would the monsters be the same, only converted to DCC? Would they be totally new monsters? Would we have a book giving stat write-ups for monsters found in the Appendix N literature? What might make this product different enough to justify its own existance.
As Hamakto sort of mentioned, the DCC core rulebook will have a list of standard monsters already, so this would be monsters on top of the "core" selection.
Marv / Finarvyn DCC Minister of Propaganda; Deputized 6/8/11 (over 11 years of SPAM bustin'!)
DCC RPG playtester 2011, DCC Lankhmar trivia contest winner 2015; OD&D player since 1975
"The worthy GM never purposely kills players' PCs, He presents opportunities for the rash and unthinking players to do that all on their own."
-- Gary Gygax
"Don't ask me what you need to hit. Just roll the die and I will let you know!"
-- Dave Arneson
"Misinterpreting the rules is a shared memory for many of us"
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