Unlike The Nun – who was the big bad in The Conjuring 2, and had an origin of sorts hinted at in Annabelle: Creation — the path for The Crooked Man going forward is a bit unclear.
Within Lorraine Warren’s revelation that the demon Valak was pulling all of the strings in the 2016 film came the suggestion that The Crooked Man was just a pawn in the whole scheme.
If that’s the case, there isn’t much established that the filmmakers can build on.
It’s possible that Annabelle 3 could wind up being useful, as the story will be set in the Warren’s museum of haunted objects that ultimately houses the spooky zoetrope in The Conjuring 2, but we’ll just have to wait and see.